Immiscible
by Dmarx
Summary: First day back from their honeymoon and someone had to find a body at – she glanced at the clock again – 5:53 in the morning? Set early season 7. Complete.
1. Chapter 1

_Author's Note: A couple months back, I challenged myself to write a case-based fic, and this is what happened. It's been a long process, but I did it. It's about 50/50 case/relationship, and there are 15 chapters in total._

_Thank you so much to Sandiane Carter for the writing advice, to Andy for always being my cheerleader and self-proclaimed bouncing ball, and to Liv Wilder, who has been a never-ending source of information and suggestions as I've navigated this new terrain._

_Disclaimer: I think we've firmly established that Castle is not mine._

* * *

**Immiscible**

_adj ~ incapable of being mixed or blended, as oil and water_

* * *

**Chapter 1**

A harsh ringing sliced through the darkness, pulling them from a deep slumber into something resembling wakefulness. Kate fumbled for her phone on the nightstand, the illuminated screen far too bright for her dark-adjusted eyes. Swiping her finger across the device, she lifted it to her ear, risking a glance at the clock as she answered. Large red numbers shone back at her, taunting her from the top of the dresser.

"Beckett."

"Hey, boss, sorry to wake you but we've got a fresh one."

Kate groaned, dropped her head back onto the pillow. First day back from their honeymoon and someone had to find a body at – she glanced at the clock again – 5:53 in the morning?

"Okay, we'll be there in a few. Text me the address?"

"You got it."

She tossed the phone aside without bothering to hit the 'end' button, rubbed her hands over her eyes. It was far too early for this. Two weeks of vacation had left her refreshed and relaxed, but the jet lag was brutal and she hadn't fully recovered. All she wanted to do was curl up next to her husband for another few hours and just sleep.

Apparently it was not to be.

"Castle."

He grunted, rolled over, burying himself further into the bed.

Kate pushed herself up onto one elbow, reached across to rest a hand on his bare shoulder. "Castle, we have a body."

"Mmmm, yes you do," he murmured dreamily, one hand reaching out for her, coming to rest on her hip.

"Castle," she chastised half-heartedly.

"Huh?"

"A dead body."

He mumbled something unintelligible but rolled onto his back, forced open one eye, then the other. "Time's it?" he slurred.

"Early."

He slipped his arm further over her, catching her around the waist and tugging her onto his side of the bed. "Mmmm, come here."

"Castle..."

"Just a few more minutes," he begged, lips at her temple, and she already felt herself giving in, relaxing into him, the desire to be in his arms winning out over the call of work.

Her phone vibrated once, signaling an incoming text message, and Kate reluctantly rolled out of his arms, picked up the device.

_Corner of Mulberry and Grand,_ it read.

"That's just a few blocks from here," Castle spoke from over her shoulder, leaning in to glance at the screen.

"Mmmm, yeah."

"You know what that means?"

"Hmmm?"

He nuzzled the back of her neck, warm breath on her skin sending a shiver racing down her spine. "We have a few minutes to spare."

"Work," she protested feebly, but the truth was that she was just as tempted as he was to shirk her responsibilities and extend their honeymoon by another few hours. The murderers of New York City always did have awful timing.

His hand slid over her stomach, fingers splayed wide across her bare skin, and she found herself surrendering without a fight, letting the warmth take over. He traced her earlobe with his tongue, tenderly nibbling the sensitive skin, and she released a blissful sigh, tilted her neck to grant him better access.

The dead body could wait.

Except...

"Castle."

His fingers danced up her side, strumming over the lines of her ribcage as his lips found the skin behind her ear.

"Castle," Kate voiced again, a little emphatic, a lot breathy.

No. She could do this. There was a murder victim waiting. A victim who deserved justice.

"Castle," she said a third time, and this time her voice was strong enough that he halted his delicious exploration of her body, lifted his head.

"Hmmm?"

She bit back a sigh at the loss of his touch, forced herself to compartmentalize. Work now. Wedded bliss later. "We have to get up."

He nudged his hips against her from behind. "I am."

"Not what I meant."

Kate rolled over and pushed herself into a seated position, running a hand through her hair as she righted herself. The sheet slipped down as she did so, revealing her in all of her nakedness, and Castle wasted no time in reaching out and wrapping a large, warm hand over her leg, fingers teasing the crease of her thigh.

She lifted off the bed slightly at his touch, couldn't stop her body's reaction to him.

He leaned in then, so close that she could feel his lips at her ear, each exhale skittering erotically across her skin. "At least let me help you wash your back."

He didn't wash her back.

He did, however, pin her against the wall of the shower.

* * *

"Hey, Lanie."

The ME lifted her head, looking up at Kate and Castle from where she was awkwardly squatting next to the body, one foot on the top stair the other one step down. They walked side by side, steps in perfect unison, shoulders brushing lightly with each step. A cup of coffee was cradled in Kate's left hand, but despite the early hour, she was glowing almost as much as the array of diamonds on her finger.

Lanie smirked, fixing them both with an expression that quite clearly stated that she knew exactly what'd gone on this morning between the ringing of Kate's phone and her arrival at the crime scene.

"Looks like you enjoyed your little vacation," she teased as Castle separated from his wife, reaching out to fist bump Ryan and Esposito, who were casually welcoming him back with a convoluted three-way handshake.

Kate couldn't help the smile that split her face, sheer contentment radiating from her eyes.

"I take that as a yes."

"Let's just say we weren't ready for it to be over," she offered. She knew Lanie wanted dish but there was no way she would be recounting any part of her honeymoon – or the way Castle thoroughly ravished her this morning – over a dead body.

Lanie raised an eyebrow. "I can see that."

"Shut up," Kate demanded around a sip of coffee, the caffeine suffusing her veins, slowly bringing her brain out of its post-sex haze and into focus on the task at hand. "So, what've we got?"

Her friend pursed her lips in disapproval of Kate's deflection but readjusted her clipboard on her lap and allowed the change of subject. For now.

"Jane Doe. No ID, wallet, cell phone, keys, nothing. Neighbor found her sprawled across the stairwell when he opened the door to grab the morning paper. Says he doesn't recognize her."

"Mugging gone wrong?" Castle mused, turning to the scene of the crime upon hearing Lanie's voice.

"Possibly."

"Time of death?"

"Based on lividity, I'd say she's been dead no more than four or five hours."

"COD?" Kate probed.

"That's where things get weird," Lanie explained. "I haven't found anything. No blood, no visible bruising. Nothing."

"Kind of shoots a hole through our whole mugging gone wrong theory."

"So does this. Guy who found the body," Ryan gestured over his shoulder at the door at the bottom of the landing. 7C, it read. "Said he'd been awake most of the night working on his computer, didn't hear a thing. No voices, no struggle, nothing, and these walls aren't exactly soundproof."

"Witnesses?"

"None so far," Esposito jumped in.

"So we can't even be sure that it's murder," Kate pointed out.

Lanie stood, rested a hand on her friend's arm. "Let me get her back to the lab, run some tests. I'll let you know if anything pops."

"Thanks, Lanie." She turned back to her team. "Let's canvass the rest of the building, and have unis talk to local businesses and anyone else who's out and about in the area. Someone had to have heard or seen something, and maybe someone'll recognize her."

"On it, boss," Ryan complied with a smile. He turned away, paused, turned back. "By the way, it's good to have you back."

Kate smiled, nodded her thanks before shifting her focus back to the body, contemplating the crime scene. If this even was where she was killed. If she was, in fact, murdered.

"So, no ID, no identifiable COD, and so far, no witnesses," Castle said finally, voicing her exact string of thoughts.

"Welcome back to reality," Kate muttered under her breath.

He shook his head, took a much-needed sip of coffee. "Harsh."

* * *

_Thoughts?_


	2. Chapter 2

_Author's Note: Can I just say...wow! Thank you all so much for the lovely reviews! I'm glad you're all so enthusiastic about this story. I apologize for not replying individually but I promise to do so when I have some spare time._

* * *

**Chapter 2**

"Oh my God!"

A strained voice at the bottom of the stairwell echoed off the walls, funneling down the narrow hallway. Kate and Castle whirled around to find a slim, dark haired young woman standing on the landing, eyes wide in shock. Her long hair was curled but mussed, short black dress slightly askew, eyes darkly lined but lip gloss long since worn off. As though she was just returning from a late night out on the town.

Esposito stepped forward automatically, one arm extended. "Ma'am, this is a police investigation, I'm going to have to ask you to..."

"Is that Jenna? What happened to her?"

Kate descended a couple of stairs. "You know her?"

"She's my roommate. Is she okay?"

Kate shook her head sadly, braced herself for the release of her next words. "I'm sorry to have to tell you this but she's de..."

"No," the young woman interrupted. "No, no, no, she can't be."

Before anyone could say more, she sank back against the wall, sliding down until she was seated on the floor. Her purse fell heavily into the space between her chest and her bent knees, and she dropped her head into her hands, sobs wracking her body, a steady stream of "no, no, no" falling softly from her lips.

Castle stood frozen in place, unable to react in any way. It wasn't the first time he'd been there when Kate delivered the bad news, but it never got any less painful to watch as someone's world crumbled around them. Especially someone so young, so clearly full of life.

Kate passed her coffee to Castle and made her way down to the landing, crouched next to the distraught girl. She cautiously reached out, rested a hand on the young woman's arm and spoke in a low voice. He watched as the scene unfolded, the girl slowly lifting her head, seeking the reassurance of Kate's presence. He couldn't make out the exact words, just the soothing timbre of her voice as she offered what comfort she could, gently calmed the girl's ragged breathing.

Ryan and Esposito silently crept up the stairs, poised to begin their canvass, leaving Castle leaning back against the wall, coffee cup in each hand and an adoring smile on his face as he watched his wife. Not for the first time did he find himself wishing he possessed even a moderate level of the compassion and empathy she so effortlessly conveyed. But he knew he never would, not in the same way, because hers was borne of loss. A loss he hadn't experienced.

He could only hope that he never would.

* * *

"What's your name?" Kate asked quietly, eyes soft.

She slim woman swallowed hard, spoke in a rough voice. "Sara. Sara Martinez."

"And Jenna was your roommate?"

Sara nodded. "For three years."

"You live in this building?"

She weakly gestured up the stairs. "In 8E."

"How did you know her?"

"From school," Sara replied. "We met our senior year at Pace. I was...going through some stuff and she was always willing to listen."

"You're graduated now?" Kate assumed, quickly doing the math in her head.

Sara nodded.

Kate dropped her hand, pulled out her notepad and pen and flipped to a blank page, poised to jot down what information she could gather. "Does she have some sort of job?"

"She's a research assistant at Rockefeller University."

"And was she at work today?"

Sara nodded. "But she got home around eight."

"And then what happened?"

"We made dinner," Sara recalled. "Then went down to the bar. We both have tomorrow off, so..."

Kate nodded in quiet understanding, waiting patiently for the girl to offer more.

Sara shook her head. "I should have gone after her."

"What do you mean?"

"We were at the bar." She gestured downstairs, to the establishment located in the bottom floor of the building. "I ran into a few friends I hadn't seen in a while." She sniffed, swiped at her tear-stained cheeks with the back of her hand. "They were heading to a different place and invited me to come with them. When I asked Jenna if she minded if I left for a while, she said it was fine. Said she was gonna head back up to our place soon. But she didn't look right."

"Didn't look right how?"

"Like she was confused. Or scared." Sara shrugged. "I'm not sure. She seemed really distracted and my friends were tugging me towards the door and..." she trailed off, ran the back of her hand across her face. "I should've stayed."

"Do you remember what time this all happened?" she asked gently.

"About two thirty, maybe?" she recalled, pulling out her phone and checking the time, as though it would help her remember.

"How much had Jenna had to drink?" Kate questioned carefully.

"Just two drinks. Vodka martinis." Sara shook her head, choked out a pained laugh. "They're her favorite. I never used to like them but she changed my mind. And now..."

Kate paused, allowed her a moment to gather herself before speaking again. "Did anything else strange happen? Did you notice anything?"

"What do you mean?"

"Just anything out of the ordinary?" Kate explained.

Sara shook her head. "I don't think so."

Kate nodded in understanding.

"And can you think of anyone who would've wanted to hurt Jenna?"

Sara shook her head again. "I'm sorry," she blurted suddenly. "I know I'm not much help."

"Anything you can think of helps," Kate assured her. "One more thing," she added quickly. "Did she have some sort of purse with her?"

"Of course. She never went anywhere without it," Sara answered, twisting her head around to survey the area. "Her purse is missing?"

"We haven't found one here."

Sara shook her head, dark eyes haunted as she spoke. "None of this makes any sense."

Silence fell as Kate rose, contemplating the information she'd just gathered. So far, she had to agree with Sara. Something wasn't adding up here.

"I just want to know what happened," the young woman whispered almost to herself, so softly that Kate barely caught her words.

She turned her head to examine the scene once more before focusing her attention back to Sara, offering a compassionate smile. "I promise we'll do everything we can to find that out."

* * *

A tour of Jenna and Sara's apartment didn't turn up much. It didn't seem as though Jenna had been home, and there were certainly no signs of a struggle. The location of her purse remained elusive as well.

As they walked around, CSU moved about, dusting for prints, fibers, anything that might indicate something out of the ordinary, but so far nothing seemed promising.

"She has a lot of knick knacks here," Castle observed, gesturing to the walls.

"Her parents are doctors," Sara offered morosely. "They moved to South America for work for four years when Jenna was about eleven. She loves to travel." She paused awkwardly before correcting herself, the word catching in her throat. "Loved."

Castle nodded thoughtfully, flicking through a stack of mail while Kate poked around in Jenna's dresser.

They finished their sweep just a few minutes later, but before stepping out, Kate crouched in front of Sara, offered a tentative smile. "I know this is difficult for you, but if you think of anything else," she pulled out a slim container of business cards from her pocket, extracted one and passed it to Sara, "give me a call, okay?"

Sara nodded numbly, fingers curling around the proffered card.

"I promise you," Kate whispered. "We're gonna figure this out."

* * *

The owner of the twenty-four hour coffee shop across the street was similarly shocked to hear of Jenna's demise, describing her as a lovely young woman who tipped generously and always had a kind smile for the baristas. After striking out yet again, they left uniforms to finish up the canvass and square things away with CSU, and headed back to her cruiser.

The ride to the precinct was spent in silence, Castle nursing his coffee while Kate navigated the early morning traffic. Sara's cries weighed heavily on her mind, the utter devastation she knew the young woman was going through.

From across the console, she saw Castle shift, reach out to brush his hand over her leg. She smiled meagerly, flicking her eyes briefly to his in conveyance of gratitude. She dropped one hand from the wheel to catch his before he withdrew, curled her fingers over his. He freed his thumb, traced a tender path over the ridges of her knuckles, a soft back and forth. It was instantly soothing and she felt herself relaxing under his touch, tension flowing out of her as things began to fall into focus.

It was just another case, she reminded herself. She could do this. They could. Just like always.

She squeezed his hand gently, eyes fixed straight ahead but a softness lining her features, a sense of confidence and determination. Out of the corner of her eye, she saw Castle smile to himself, unable to tear his eyes away from her even as hers remained focused on the road.

Not a word passed between them the entire ride, but none were needed.

She knew he understood.

* * *

When Castle approached her desk with fresh mugs of coffee, Kate was busily setting up the murder board. A blank timeline stretched across the bottom, and the top section was divided into three sections; victim, witnesses, and suspects. So far, all three were empty.

She reached behind her to retrieve the picture of their victim from the crime scene, clipped a magnetic clip to it and placed it front and center. Castle paused as she worked, eyes automatically drawn to the sparkling ring on her left hand. She made it a habit not to wear her engagement ring to work, preferred to keep it out of harm's way. But she hadn't taken the slender diamond-encrusted platinum band off her finger since he slipped it on two weeks ago. This ring was smaller, flatter, and the inlaid stones easily fit beneath the latex gloves they wore at crime scenes. He'd chosen it in part because it was much more precinct appropriate, something she could wear every day.

Because they were married now.

He was never getting over that.

Kate turned, fixing curious eyes on her husband, who was still rooted to the spot, gaze unfocused as if in a trance.

"Castle?"

He jerked, shook his head to clear his mind. "Sorry, just..." he extended his left hand, "coffee?"

She took it from him with a gracious smile, fingers brushing his as they exchanged the vessel. Castle allowed his hand to linger, thumb stroking her wrist, a soft whisper of a touch. Kate dropped her eyes to their hands, flicked them back up to seek Castle's gaze. His eyes were dark, desire and lust and pure love swimming in their depths, and she had to look away.

Kate raised the coffee mug to her lips and took a long drink. It was hot, too hot, and it burned down her throat, but the sensation had the desired effect of intercepting her heady train of thought, returning her focus to the case. They had a murder to solve, justice for a young woman.

She lifted her eyes again to find Castle's fixed firmly on her chest. As though if he stared hard enough he'd be able to see the black lacy bra she'd slipped into this morning even as his fingers worked very hard to remove it again. A shiver of arousal rippled through her and she forced herself to look away, squeezed her eyes shut. Tightly.

He couldn't look at her like that and expect her to get any work done.

* * *

_Thoughts?_


	3. Chapter 3

_Author's Note: Apologies for the delay - this site has been acting up pretty badly lately. In case you didn't get the alert for chapter 2, you should probably jump back and read that one first. _

* * *

**Chapter 3**

"Hey, guys," Castle offered in greeting.

Beckett lifted her head in time to see Ryan and Esposito approaching her desk, fresh off their early morning canvass and clearly engrossed in an animated debate.

"Hey, anything?" Kate called as they neared.

"A whole lotta nothing," Espo answered, tossing his jacket over the back of his chair as he walked by. "Talked to some of the neighbors but no one seemed to know much about Jenna or Sara. Seems they mostly do their own thing."

"Didn't get the feeling that anyone in the building was particularly talkative. Few people said they'd passed her in the hallway," Ryan elaborated. "Said they'd exchange 'how are yous' in the laundry room, but that's about it."

"According to the super, they've lived there about eight months," Espo added. "Said they always paid rent on time and no one had filed any complaints."

"No one heard anything last night?" Castle questioned.

Esposito shook his head. "One guy recalled hearing a couple guys duking it out on the sidewalk about midnight, but that's before our time of death."

"Huh," Castle mused.

Ryan removed his jacket, draped it over his arm and nodded to the murder board. "What've you guys found?"

"Jenna Mays, twenty four," Beckett began, rolling her chair back and rising to her feet as she spoke. "Biomedical research assistant at Rockefeller University. Not much else at this point except what we know from Sara."

"Anything from Lanie on COD?"

A shake of her head. "Not yet."

"So we have almost nothing to go on," Ryan stated.

"I put in a call for phone records and financials, and unis are tracking down next of kin," Kate rattled off. "But I haven't found much else."

Ryan nodded thoughtfully.

"Bar was closed and we haven't been able to get ahold of the owner, but there's a traffic cam across the street," Espo added. "It's a long shot, but," he shrugged, "footage is on its way."

Kate took a sip of coffee, paused as the liquid slid down her throat. "It's worth a try."

"So," Castle drawled as the boys turned back to the board, collating what little information had appeared while they were away. He perched in front of the murder board, one butt cheek resting against her desk, coffee cradled in both hands. "How do we investigate a murder when we don't even know if she was murdered?"

"What, no wild theories about invisible bullets and secret assassins?" Kate teased.

Castle shrugged. "Guess not."

"Come on bro," Espo called, tossing a smirk over his shoulder as the boys headed off to track down the video footage. "Stolen purse and a mysterious COD? You should be all over that by now."

"I can think of something I'd like to be all over," Castle uttered sexily, low enough for only Beckett to hear.

She narrowed her eyes in disapproval but couldn't completely suppress the flutter in her tummy or the pink that stained her cheeks. Damn him and his ability to make her lose all train of thought.

"Beckett?" called a voice from behind her.

She startled, took a moment to compose herself before turning. "Yeah?" She hoped she sounded more focused and professional than she felt.

"Parents are here."

She sobered instantly, setting aside her coffee mug and pausing to take a deep breath.

"What are we gonna tell them?" Castle asked, standing and following her to the interview room, all traces of teasing gone.

She tossed a glance over her shoulder, lips narrowed grimly. "As much as we know."

* * *

"Hey, Lanie."

"Hey," the ME greeted, finished signing her name across the bottom of a medical form before turning her attention to Castle and Kate.

"Anything?"

Lanie stood, crossed the room to retrieve the proper file. "Well, nothing visible to suggest foul play. No bruising, no signs of struggle, but I'm officially putting time of death between two and four a.m.."

"Cause of death?" Kate asked.

"I'm still waiting on lab results," Lanie reminded her. "But in the meantime, I did find something weird during the autopsy."

"Do tell," Castle prompted excitedly.

"Edema," Lanie announced, paused then elaborated. "Fluid accumulation. Particularly around her airways."

"And what does that signify?" Kate inquired.

Well, it's most often seen in people with congestive heart failure," Lanie explained.

"In a twenty-four year old?" Castle interjected.

"That's what I thought."

"Huh."

"Also, her heart was almost empty."

"Empty...as in there wasn't any blood?"

Lanie nodded. "Exactly."

"And what could cause that?" Kate questioned in interest.

"A drastic drop in blood pressure," Lanie answered. "It's most often caused by severe blood loss, though that obviously wasn't the case here."

"Anything else?"

"Off the top of my head? Heart conditions, infections, and extreme cases of dehydration," the ME recited.

"Edema and dehydration?" Castle wondered aloud.

"Not usually concurrent," Lanie agreed.

"Did she have heart problems?" Kate asked.

The ME shrugged and shook her head. "Medical records haven't come in yet. Has anyone you've interviewed said anything about health conditions?"

"Nope. Parents didn't mention anything, but we also didn't ask."

"So it wasn't murder?" Castle asked.

Lanie shook her head. "I don't wanna make the call until the tox screen comes back, but as of right now..."

"Can something else manifest in a similar way?" he asked, grasping for an explanation. Something wasn't lining up here, but it couldn't quite put a finger on it. "Maybe from the alcohol. Or drugs? Could she have OD'd?"

"If she did it'll be in the tox results," Lanie answered.

Kate thanked her friend, turning and heading for the door, but not before catching sight of Lanie's silent demand for girl time. She nodded in understanding, allowed Castle to guide her from the morgue with a hand spanning her lower back.

Girl's night would have to wait. For now, it was time to head back to the precinct.

* * *

The elevator dinged, signaling their arrival on the homicide floor, and Ryan was on his feet the moment they stepped out of the elevator. "Anything from Lanie?"

Kate shook her head. "Nothing to suggest foul play. How about traffic cam footage?"

"It's a poor angle on the entrance of the bar, but from what we've seen so far, there's nothing suspicious," Esposito piped up, falling into step next to them.

They reached Kate's desk and she removed her jacket, draping it over the back of her chair before crossing one foot in front of the other and folding her arms across her chest.

"What'd Lanie say?" Ryan asked.

Castle recited the ME's findings while Kate reached for a marker, jotted some new notes on the murder board.

"But it's possible it was murder?" Ryan questioned as Castle finished his recap.

"We don't know yet," Kate answered.

"Phones and financials came in while you guys were out," Espo added, extending a stack of folders to Castle.

She turned her head, glanced at the pages of print over her husband's shoulder. "Anything?"

He shook his head. "No unusual activity."

Kate added this information to the white board, the neat strokes of her penmanship flowing smoothly from one letter to the next, marker squeaking lightly against the glossy surface. "This is looking more and more like it was just a tragic death."

"It can't be," Castle countered. "It just doesn't make sense."

Espo shrugged. "Sometimes people die, bro."

"Yeah, but a twenty four year old who by all accounts was healthy, hard-working, and well-liked?"

"Doesn't make her immortal."

"I know, but something doesn't add up."

"Does anyone else find it odd that her purse was stolen the same night she died?" Ryan interjected, gesturing to the murder board.

"Exactly," Castle spoke up. "If her death was accidental, what happened to her purse?"

"Maybe she lost it," Espo offered.

"And then dropped dead?"

"Maybe someone stole it from her body," Kate suggested.

"So someone just happened upon her dead body on their way up the stairs and decided to take her purse?"

She shrugged. "Wouldn't be the strangest thing that's ever happened."

"But we spoke with almost everyone in the building, and most people said they were asleep around the time of death," Ryan reported.

"Doesn't mean they were telling the truth."

She paused, turned. "Castle, why are you so convinced this was a murder?"

"It just doesn't make sense otherwise."

Kate capped the marker, deposited it on the tray at the base of the board. "Come on," she encouraged. "We won't have anything else from Lanie until tomorrow at the earliest. And let's face it. We really don't have anything to go on. Let's call it a night."

Ryan and Esposito didn't need telling twice, returned to their desks to shut down computers and pack up their things. Kate collected the file folders, crossed the bullpen to store them away for the evening. When she returned, Castle was still surveying the murder board, a look of concerned determination on his face.

"Hey," she called softly, pulling his focus away from the case. "You ready?"

He nodded rapidly, turned. "Yeah, yeah, of course."

She smiled, snagged her jacket and tugged it on. Castle automatically reached out to untuck her hair from her collar, straighten the fabric.

"Thanks," she murmured with a smile, pocketing her phone and keys and grabbing her bag from the floor.

Castle trailed her to the elevator, standing silently with his hands in his pockets as they descended. Kate threw a concerned glance in his direction, received a wan smile in return. He kept up a mindless conversation on the drive home, even managed to crack a few laughs.

But despite it all, Kate couldn't shake the feeling that something wasn't quite right.

* * *

_Thoughts?_


	4. Chapter 4

_Author's Note: A little break from the case here, for those who are looking forward to some Castle/Beckett goodness. _

* * *

**Chapter 4**

When Castle climbed into bed, back against the headboard and eyes staring blankly at the wall, Kate finally broke the ice.

"Hey, you okay?" she probed, gently nudging his shoulder with her own.

He shrugged, fiddled with the hem of his t-shirt. "Just this case."

Kate straightened her legs beneath the covers, rolled onto her side and propped herself up on one elbow. "What about it?"

Another shrug but no verbal response.

"Castle."

His eyes shifted to his lap, following the absent-minded motions of his fingers as they teased the edge of the fabric, pausing on a small irregularity in the stitching. "It's nothing."

"Rick," she chastised lightly.

"I just...we're missing something."

"Like what?"

"I don't know," he countered, still unwilling to meet her eyes. "But we have to be. It's the only story that makes sense."

"No, it's not," Kate disputed. "And you know that. So what's really going on here?"

His fingers twisted in the fabric, bunching the material in agitation. "People her age don't just drop dead."

"Sometimes they do."

"I know, but. Just," he sighed heavily, tipped his head back, eyes staring unfocused at the ceiling. "She's not that much older than Alexis."

Oh. Right. Kate's stomach sank. She should've made the connection sooner. Sure, there was a bit of an age difference, and the girls hailed from drastically different backgrounds. The dark auburn of Jenna's hair was clearly from dye and her eyes were green rather than blue. Nevertheless, the similarities were there, and Kate silently reprimanded herself for not catching on sooner.

"Castle," she soothed, rested what she hoped was a calming hand on his arm. She may have missed the initial signs, but at least she could be here for him now. "Nothing's gonna happen to Alexis"

"I'm sure that's what Jenna's family thought too," he protested, and the pain in his voice struck low in her gut. He finally turned to look at her and she could see the hurt darkening his eyes, the deep-seated empathy he felt for this family. "And now she's just - gone. And if something happened to Alexis..."

Suddenly he was turning away, reaching for his phone. He swiped his finger to unlock the screen, was abruptly halted by a hand on his arm even as he scrolled through his contact list, selected a name that clearly wasn't his daughter's. Kate snatched the phone from him, pulling it away from his ear and ending the call before it had a chance to go through.

"What're you..."

"It's ten o'clock at night," she reminded him as she glanced at the screen. "And who's Dr. Jacobs, anyway?"

"Alexis's pediatrician. I mean, I know she's not a little girl anymore, but any doctor can do the tests, right? And..."

"Whoa, whoa, whoa, what tests?"

"I..." he stammered uselessly.

"Castle, Alexis is fine," she assured him in a low voice. "She's perfectly healthy, and..."

"You don't know that."

"I..."

"I just think she should get checked out," Castle justified.

"Okay," Kate conceded. He had a tendency to be overprotective and she knew there was nothing she'd ever be able do about that. "But maybe you can wait until morning to schedule an appointment for her?"

He sighed, relented, his shoulders sagging in defeat. "Fine."

"I promise you," she whispered, offering a gentle smile. "Alexis is perfectly healthy."

"You can't promise that."

And sadly, she knew he was right. She couldn't promise a healthy future for his daughter any more than she could promise to come home safely every night. It was the danger of her job. A fact of life.

But there was one thing she could do that might help. For now, at least.

* * *

"Hey, Dad,"

"Actually, it's Kate."

"Kate," Alexis greeted happily before her brain seemed to take off in a different direction. "Wait." Her voice faded, as though she'd pulled the phone away from her ear to double check. "This is Dad's phone. Is everything okay?"

"Everything's fine," she promised hastily. "Just a bit of a rough day back at work."

"A case?" the girl asked. She'd shown an increasing interest in Kate's work ever since the Innocence Review project she'd been a part of last year. It'd certainly been a turning point in her relationship with Castle's daughter, a foundation on which to begin building.

"Mmm," the detective answered, sought Castle's gaze as she spoke. "Your dad's taking it kind of hard. I think he might like to hear your voice."

At Alexis' affirmative answer, Kate smiled gently, held out the phone to her husband.

She stuck around for the first couple minutes of the call, long enough to watch the light begin to return to Castle's eyes. When it became clear that their conversation was far from over, Kate lightly patted his thigh, slipped from the bed, and padded out to the kitchen. She pulled a glass from the cupboard, filled it from the tap and took her time sipping the cool liquid. She meandered over to the window with the beverage, stopping in front of the wide pane and taking in the view, the Manhattan skyline glowing and the streets below alight with activity.

The kitchen light illuminated just enough that she could see her own reflection shining back at her too. It was faint and slightly distorted by the glass but despite that, she could see the smile in her eyes, the glow of her features. She was happy. Completely, radiantly happy. Castle had always made her happy, long before she was willing to admit it, but this was something more.

And maybe some of it was leftover from their blissful honeymoon, but it wasn't just that. Sure, they'd already lived together, were already basically married prior to the actual ceremony. Hell, in many ways they'd behaved like married couple long before their engagement.

But now it was different. Now they'd promised each other everything. Forever.

A broad smile split her face.

Professionally, she was still Kate Beckett. And after less than three weeks, it still sounded strange to her own ears when she introduced herself otherwise.

But she had to admit, Kate Castle had a nice ring to it.

* * *

As the soft hum of Castle's voice faded from the air of the loft, Kate set her water glass aside, switched off the light and made her way back to him. She couldn't hear what'd been said, but from the more upbeat lilt of his voice as the conversation had progressed, along with the soft smile on his face as she re-entered their bedroom, she could safely assume things had gone well. He certainly seemed to be much more calm and relaxed.

"Thank you," he murmured as she slipped back into bed, head tilted in her direction, eyes deep with earnestness.

Kate merely offered a smile, situated the covers over herself and reached out to switch off her lamp. Castle, however, wasn't satisfied with her response, and he leaned over, caught her lips in a kiss full of gratitude.

"No really," he reiterated as they separated. "Thank you."

She blinked open her eyes, found his penetrating gaze locked on her. "Anytime."

* * *

It wasn't the first time a case had hit close to home, and Kate wasn't nearly naïve enough to think it would be the last.

It was, however, the first night since the wedding that they fell asleep fully clothed.

* * *

_Thoughts?_


	5. Chapter 5

_Author's Note: To those whom I didn't have a chance to reply individually - thank you so much for the reviews!_

_Delving back into the case a bit this chapter._

* * *

**Chapter 5**

"What's in the folder?"

"CSU report from the crime scene," Kate answered automatically, eyes never lifting from the page as she scanned the findings.

"Anything?" Castle asked, his voice much closer now.

She looked up, passed him the file in exchange for one of the steaming mugs of coffee cradled in his hands. "Nope. No blood, no prints, nothing. If this was murder, she wasn't killed there."

Castle took a sip of the hot liquid, lowered the mug slowly as he contemplated the report.

"But her body didn't show any signs of being moved."

"Mmm, true."

"Hmmm," he ruminated, setting aside his coffee, freeing both hands to flip through the rest of the report. He pursed his lips as he scanned the pages, searching for any unusual bit of information. But after a couple minutes, he had to admit that nothing was jumping out at him.

Huh.

While Castle was heavily engrossed in the report, Kate fired up her computer, turned to eye the murder board while she waited. Not that she expected anything new to have appeared overnight but...

Wait.

She whirled around. "You guys talked to the bartender?"

"Yeah, owner returned our call last night right after you guys left," Ryan clarified, rising from his desk and making his way to them. "We were able to track down the bartender as well as a few regulars."

"Anything?"

"As a matter of fact, yes," Espo announced, jogging over. "Regulars didn't have much to say except that they'd seen her there on occasion, usually with Sara."

"But apparently she _did_ say something to the bartender about a purse," Ryan recalled. "Asked if he'd seen one."

"So it was stolen at the bar, not from her body," Castle pieced together, setting aside the CSU folder and tuning into the conversation.

Esposito raised one shoulder in assent. "Seems like it."

Kate turned back to the murder board, considered what they knew. "Anything else?"

"Said she disappeared pretty quickly after that. Made a beeline for the door."

"She ran?"

"So it would seem."

"But from what?"

"Whatever it was that freaked her out," Castle suggested.

Kate tilted her head. "What do you mean?"

"You said Sara said she looked confused or scared, right?"

"Probably because her purse was missing," Kate pointed out.

"Then why didn't she say anything?"

"Good point," Ryan piped up. "You'd think she'd have told Sara.

"Maybe she hadn't noticed it yet," Kate theorized. "Think about it. Sara tells her she's gonna take off with her friends, Jenna turns to grab her purse and head back upstairs, only to realize it's gone. She panics, asks the bartender, and when he says he hasn't seen it, she runs to try to catch up with the roommate."

"Mmm, she would've gone outside, not upstairs," Esposito pointed out.

"And if that's the case, why did something look off _before_ Sara left?" Castle pointed out.

"Maybe she saw something?" Ryan suggested, approaching it from a different angle. "And that's _why_ she decided to leave."

"Maybe Sara isn't remembering correctly," Kate pointed out. "It's a bar. It was probably loud and dark. And she'd been drinking."

"Yeah, but forgetting a detail and thinking something is wrong with your friend are two different things," Castle argued.

"I admit it's an odd thing to misremember," Kate conceded, not sure what else to say on the matter.

Her phone chirped from behind them, signaling the arrival of a message, and she retrieved the device, unlocked the screen.

"What is it?" Castle asked, leaning in to glance over her shoulder.

She gestured with the phone. "Lanie. Tox report just came in. Apparently there's nothing out of the ordinary."

"How can there be nothing?" he exclaimed in irritation, reaching for the phone. "Let me see that."

She pulled the phone away from his grasp, shot him a halting look. "It's just a text. Report is on the way over."

"Oh. Right." Castle sighed, dropped into his chair with a dramatic flop.

Kate shook her head, settled into her own chair and opened her email. The tox report hadn't done anything to back their theories, meaning all they had to go on at this point was a supposedly stolen purse, which, while coincidental, didn't exactly scream murder. For all they knew, she'd simply misplaced it and it'd disappeared into the chaos of the Friday night bar scene.

But for Castle's sake, Kate almost found herself wanting it to be a murder, if only so he'd stop worrying so much about Alexis. Not that the murder of a twenty-something woman would ease his conscience either. She supposed it was only natural, the protective instincts of a father.

Maybe someday when they had kids, she'd understand.

Whoa. Wait.

_Slow down, Kate,_ she scolded herself. They'd been married less than three weeks, and she was already thinking about kids?

No. Just. No. Not for at least another few months.

She shook her head to force the thought from her mind, focused on combing through her new messages. Nothing of importance, but at least it would keep her mind occupied until the full tox report arrived.

* * *

"Hey, guys," Ryan greeted, stepping off the elevator and hustling towards them.

Castle and Esposito paused their conversation, turned to greet their partner.

"Nice purse," Castle japed, received an approving pat on the shoulder from Espo.

"Yeah, haha," he shot back, unfazed. "It's Jenna's."

Kate lifted her head sharply. "Wait, what?"

"Unis found it in a dumpster near the bar." He reached inside with a gloved hand, extracted her wallet. "ID inside is a match to Jenna."

"Her wallet's still there?"

"Mmhmm, along with her cash, credit cards, keys, and phone. Doesn't look like anything was taken."

"Where'd they find it?" Kate asked, getting to her feet and crossing to the murder board. She uncapped a marker, began filling in the blanks on the murder board.

"In an alley off Mott Street, mixed in with a bunch of old Chinese food."

"No wonder it smells like egg rolls," Castle joked.

Esposito wrinkled his nose. "That's gross, bro."

With a grimace, Ryan slipped the wallet back into the knockoff leather purse, dropped the whole thing into an oversized evidence bag. "I'm just gonna," he tilted his head to the side, "pass this on to CSU."

Kate nodded her approval, turned back to the board to complete her sentence. Esposito headed off in the direction of the break room to refill his coffee, leaving Castle sitting in his chair, once again contemplating the facts at hand.

"So. Hmmm."

Kate turned, regarded him curiously.

Castle cocked his head. "You know what still doesn't make sense to me?"

"What's that?"

"Why would you mug someone and get away with it only to come back and kill them?"

"We don't know that anyone _killed_ her, Castle."

He held up a hand, conceding her point. "Okay, but let's say that someone did. Why would you steal her purse and risk getting caught by coming back to kill her?"

"That's assuming it was the same person."

"Well what are the odds of having someone steal your purse and then getting murdered on the same night but by a different person?"

"Mmm, true," Ryan agreed, reappearing sans purse.

"So our thief and our killer are one and the same?" Espo rejoined the group, sipping from a fresh mug of coffee.

"But why kill her? I mean, he got what he wanted, right?"

"But nothing was missing," he stated.

"Maybe he found something in the purse," Ryan tossed out.

"Like what?" Kate prompted.

He shrugged. "Drugs. Money. Any number of things."

"Blackmail," Castle suggested eagerly, the story already forming in his mind. "Picture this. He's being blackmailed, though initially he's not sure by whom. He does his research, narrows it down to Jenna, and then steals her purse when she's not paying attention. Inside, he finds what he's looking for. Maybe it's photos, maybe it's information. Whatever it is, it's enough for him to realize that she's the blackmailer."

"And so he kills her?" Ryan questions. "He had the materials, why not just lock them up somewhere?"

"Maybe that wasn't all of them," Castle suggested. "Or maybe he's afraid there're additional copies somewhere."

"Or maybe he _didn't_ find them in the purse," Ryan considered.

"He had her keys, why not toss her place?" Kate asked.

"You guys were there, right? Said everything was fine?" Ryan asked.

"Yeah, and CSU said the lock hadn't been tampered with," she recollected.

Castle shrugged. "Maybe he didn't want to risk getting caught?"

"Guys, you're forgetting one thing," Esposito cut in. Three sets of eyes turned to him in interest. "Nobody 'came back,'" he curled his fingers into air quotation marks, "to kill her. And we haven't talked to a single person who witnessed anything out of the ordinary, except for her suddenly running out of the bar."

"Is it possible someone followed her?"

"Not from what anyone's said."

"And even if they did, we still don't know how they killed her."

"There's really nothing on the body?" Castle questioned.

"You read the CSU report."

"I know, I just. This case is so frustrating."

"Maybe that's because we're making it into a homicide when it really isn't one," Kate suggested.

"So Jenna, by all accounts a lovely, friendly, healthy young woman," he ticked off the points on his fingers as he spoke, "gets her purse stolen from the bar, abruptly rushes out, and then drops dead on the stairs up to her apartment?"

"I admit it's an unusual string of events," Kate agreed. "But if she died of natural causes, we don't have any grounds to investigate it as a murder."

Castle shook his head, unconvinced. "There has to be something else. Twenty three year old women don't die of heart failure."

"I don't know what to tell you, bro. It's all right here."

"Well there has to be something." Castle reached for the file but Kate was faster, snatching the folder from Esposito's grip and flipping it shut.

"You guys," she stated, features sharp and determined. "We have no cause of death, no evidence of foul play. I think it's time to consider that maybe this wasn't a murder. Maybe she just...died."

* * *

_Thoughts?_


	6. Chapter 6

**Chapter 6**

Much to Castle's dismay, Kate spent the rest of the afternoon filling out paperwork and preparing to dismiss the case. Jenna's death had officially been ruled as natural causes - tragic, no doubt, but displaying numerous signs consistent with those of congestive heart failure. Though it was incredibly rare in someone of Jenna's age, it wasn't unheard of. And with nothing from the tox screen or final autopsy report, they didn't have the grounds to declare it a homicide.

Despite his efforts, even Castle had to admit that there wasn't much to suggest foul play. Unless CSU found something on the purse, they had almost nothing. Maybe it really was just a coincidence.

Statistically unlikely. Very much so. But he was reluctantly willing to concede that it was in fact possible.

Still, he couldn't shake the feeling that there was something they were missing. Maybe something that wasn't picked up by the tox report, he silently wondered. There were poisons designed to cheat the system, right? Castle dug his phone out of his pocket and opened the browser app to do a bit of research, completely losing track of time as he found himself enmeshed in the world of lethal poisons and various substances chemically engineered to evade detection.

None of them particularly appeared to line up with Jenna's post-mortem conditions. However, he soon found himself laden with all sorts of ideas for the next Nikki Heat novel. An undetectable poison administered by an enigmatic assassin, leaving Nikki and Rook to track down the killer. He'd call it _Venomous Heat. _And he'd give Lauren Parry a chance to shine, have her be the one to uncover the mystery. There'd be something in the tox screen to indicate an accidental death. Maybe an overdose, maybe an unfortunate combination of medications. Maybe a poison of some sort. Something someone snuck into her food.

Wait. Sara had said that Jenna worked in a medical research lab. Her parents had said something about her studying the immune system. He couldn't recall all the medical terminology but regardless, a lab like that had to be full of potential powerful toxins.

He needed to examine the autopsy report again.

Kate nearly fell out of her chair in surprise when Castle suddenly jumped to his feet, phone in hand as he hurried across the bullpen, a pleased smile on his face. Whatever he'd been doing on his phone for the last two hours, he'd been unusually silent and secretive about it, and she couldn't help but feel suspicious.

He was obviously up to something.

* * *

"Hey."

Castle startled, whirled around, hot coffee sloshing over the edge of the mug and onto his thumb.

"Ow, ow, hot," he gasped, sucking the finger into his mouth in an attempt to soothe the burn.

"Sorry," she murmured, stepping up next to him and taking over the coffee duties while Castle rushed to turn on the tap and run a stream of cool water over his finger. Kate poured coffee into the other empty mug he'd set out, stirred a bit of creamer into each and added a small spoonful of sugar to Castle's mug as well. She tossed the stirrer into the garbage, lifted her mug to take a drink.

"Finished the paperwork?" he asked pointlessly as she set mug back onto the countertop.

"Mostly," she answered with a half-shrug. "Finished whatever you were working on?"

"What d'you mean?"

"You were practically glued to your phone for two hours."

"Oh, that," he answered easily. "Just doing some research."

Mmmm. Right. Of course he was.

Kate raised an eyebrow disbelievingly. "Nikki Heat?"

He shrugged, turned off the tap and held his thumb up for examination. "Possibly." He bent the digit, winced as the reddened skin stretched over his knuckle.

"Let me see," she murmured, gently grasped his wrist, holding his hand in place as she stepped into his personal space. She could see where the liquid had spilled, and the area was a bit inflamed, but nothing he wouldn't bounce back from fairly quickly.

"Kiss it better?" he asked with a mock pout, fixing her with his most convincing puppy-dog eyes and batting his eyelashes. Completely adorable. And completely inappropriate for the workplace.

"We're at work."

"But it hurts."

She dropped his hand, rolled her eyes in an attempt to repress her body's reaction to him. "It's just your thumb. You'll survive."

"But it's my right thumb," he pointed out, as though this made some sort of difference.

"So?"

"So I'm right handed."

"Again, so?"

Castle reached out, settled his left hand on her hip, fingers splayed wide, thumb tracing the ridge of her hipbone. "So I seem to recall you being rather fond of my fingers," he articulated in a low voice, left thumb sliding lower, dipping beneath the fabric of her pants. "Particularly my thumbs."

Her hips instinctively twitched into his touch as his nail scraped along the edge of her underwear before withdrawing. A pleased smile split his face as she leaned into him, chasing his fingers even as he dropped his hand, shoved it firmly into his pocket. He stepped back, picked up the mug of coffee, and headed for the door, leaving Kate frozen in place, every fiber of her being strumming with unquenched arousal.

Damn him and his sinfully talented fingers.

* * *

She couldn't stop staring at his hands. The movement of his thumbs over the touch-screen keypad on his phone. The dexterity as he twirled the white board marker between his fingers, absently spinning the writing implement around and around. The tapping of his thumb against his pant leg as he studied the murder board that she hadn't yet taken down, unwilling to relent in his determination to find Jenna's killer.

And she should've been helping him. She should've been rechecking financial records and digging up any background on Jenna, because Castle was right. Something didn't add up.

But all she could think about was the soft touch of his hands on her skin, the thickness of his fingers, the way he could so easily reduce her to a quivering, helpless mess with just the work of his hands.

Just the thought of it made her tightly cross her legs, a not-so-discreet attempt to disguise the intensity of her body's reaction to him.

Five o'clock could _not_ come soon enough.

* * *

By the time they arrived at the loft, Kate was so riled up that she pressed him back against the door, slamming it shut with his back as she practically climbed his body.

"A little eager, are we," he teased with a saucy smirk, hands spanning her ass as she hoisted her legs up and locked them around his waist.

"Shut up."

Her fingers found the buttons on his shirt, deftly slipping each tiny disk through its hole until her hands could slip beneath the fabric, spanning warm and wide over his chest. He turned them around, pressing her back against the door as she pushed the shirt over his shoulders, tugging the sleeves down his arms, and he released his grip on her one hand at a time to allow the garment to fall to the floor.

Kate was just loosening his belt when her phone vibrated in her back pocket. Her hips instinctively bucked into Castle's and he groaned, dropped his head to her shoulder.

"Ignore it," he demanded, voice rough with arousal.

She sighed, dropped her head back against the door as she unwound her legs from their iron grip on his waist. "I can't."

She extracted the phone, a frustrated sigh escaping at the _12th Precinct_ flashing up at her. Kate cleared her throat, answered the call.

One look at her face said all he needed to know.

The case on Jenna being all but closed meant that they were once again available and on call for the next unlucky victim.

And it looked as though he or she had just been found.

* * *

_Thoughts?_


	7. Chapter 7

_Author's Note: Thank you everyone for your comments & reviews. I love hearing your thoughts about the case. Keep them coming!_

* * *

**Chapter 7**

The case was just as baffling as the last. A young woman found slumped in a stall in the woman's restroom at a sports bar off Houston. No blood, no visible markings. Nothing.

Except this time, her purse was fully intact.

"Is anyone else seeing the similarities here?" Castle mused, poking his head into the other bathroom stall to look around.

Kate whirled around, shoving one hand into a latex glove as she spoke. "To what?"

"Young woman slumped over dead. No visible COD, no signs of struggle," he ticked off each point on his fingers. "Not to mention the fact that we're just a few blocks from the other crime scene."

"You think they're related?"

"Well, what are the odds?"

Before Castle could answer, the door swung inwards, notes of an animated conversation preceding the individuals to whom the voices belonged. "Bro, it's a woman's bathroom."

"What, you afraid you'll lose your masculinity?"

All eyes turned to them as Ryan and Esposito entered, and they paused their conversation, heads turning from side to side.

"What?" Ryan asked harmlessly.

Kate huffed a laugh and shook her head before stepping aside to allow the ME to bring them up to speed.

Lanie consulted her clipboard. "Annalise Franklin, twenty four. Patron came in to use the facilities and found her sprawled here against the wall."

"COD?"

"Nothing so far, though she appears to have thrown up just before she died." Lanie gestured over her shoulder to the toilet. "Judging by how busy the bar is, I'm guessing she hasn't been dead long."

"What was she doing here?" Espo asked.

"Eating a burger and watching the game with her boyfriend." Kate nodded toward the door. "Ernesto Garcia. Unis are talking to him now."

Castle and Kate spoke with the staff while CSU finished their work, and by the time they'd headed back to the precinct and spoken with Annalise's parents, it was closing in on nine p.m. Despite the urge to stay and begin digging into the life of their vic, the team decided to call it a night, head home for some sleep.

Nevertheless, it was nearly ten when they finally arrived at the loft with the deli sandwiches they'd grabbed on the way home. Kate closed and locked the door, tiredly leaned back against it as she wriggled out of her boots, released an exhausted sigh. Four days ago, they'd been wrapped up in luxurious sheets in a swanky hotel. Now here they were, thoroughly exhausted and tangled up in not one, but two cases in the same day.

She much preferred the former.

Castle was already in the kitchen, pulling down plates and retrieving their half-finished bottle of wine from the refrigerator. Kate slipped off her coat and tossed it onto the sofa, too lazy to hang it in the closet, and joined him at the bar. He greeted her with a glass of wine and a plate containing her unwrapped sandwich, and she took it with a tired smile and quiet 'thank you.'

Dinner was hurried and shrouded in silence, merely focused on attending the basic needs of food followed by sleep.

Half an hour later found them crawling into bed, sharing a brief goodnight kiss before extinguishing the lights and succumbing to their exhaustion.

Kate fell asleep with Castle's arm heavy over her waist, his face nuzzled into the back of her neck, both of them fully clothed.

Again.

* * *

Annalise's death, as they promptly discovered the next morning, wasn't at all straightforward.

Seven thirty a.m. found Kate frantically stumbling into the clothes that Castle had been doing his best to prevent her from putting on, while the man himself dashed to the bathroom for a hurried shower. Her damp hair was thoroughly mussed from the tangle of his fingers; she hastily tied it back into a bun before dabbing on a bit of makeup that would hopefully help to tamp down the heat in her cheeks and heady darkness of her eyes.

By eight, they were sliding into her cruiser, Castle sitting on his hands to stop himself from reaching for her, Kate biting down on her lip and forcing herself to focus on the road.

They were so busted.

* * *

"Hey, Lanie."

The door to the morgue swung open, revealing a slightly flushed Kate and a tousled Castle striding along behind her, both trying – and failing – to appear focused and professional.

Lanie gave them a pointed once-over, silently raised an eyebrow. Kate leveled a glare at her friend, but next to Castle's still damp hair, the gesture was completely ineffective. She unsubtly wiped the back of her hand across her mouth, a futile attempt at removing the taste of their rather passionate kiss from her lips. It didn't help; after the last three weeks, she was fairly certain that Castle was permanently infused into every cell of her body.

"Prolonging the honeymoon again, I see," Lanie sassed.

"Shut up."

"I'm just saying..."

"You said you found something?" Kate interrupted, forcing the conversation away from their less-than-PG elevator activities and back to the case at hand. Whatever the ME had found, it'd better be good enough to have warranted the interruption of Castle's seductive exploration of her body in what had been well on its way to becoming one of their more passionate bouts of morning sex.

"I found internal signs of asphyxia," Lanie began, "but there are no visible signs of strangulation. No bruising, no signs of a struggle."

"What does that mean?"

She shook her head. "Not sure. Tox results came back negative, but I'm running some more tests just to be sure."

"You think you know what happened?" Castle asked perceptively.

"Two vics, no visible COD and nothing in the standard tox screen?" she recited.

"Poisoning?" he guessed.

"I think that's the most likely culprit. Something a standard tox screen wouldn't necessarily catch." She turned back to Kate. "Given the odd nature of these deaths and the proximity of the crime scenes, I'll run them on both vics, see if anything pops."

"Okay, thanks Lanie."

She nodded, turned back to her work as Castle and Kate made their way out of the morgue, the doors swinging shut in unison behind them.

"They have to be connected," Castle stated as they headed off down the hall, steps perfectly in sync.

She turned her head in agreement. "I think you're probably right, but..."

"I'm sorry, what was that?" he interrupted. "I'm what?"

"What?"

"Repeat what you just said. I'm what?"

Kate retraced her words, pursed her lips in disapproval. "Shut up."

Castle pulled out his phone, quickly called up his recording app and held the device up to her mouth. "No, please, say that again. So I have it on record for future reference."

"In your dreams. Now, as I was saying," she continued, brushing aside his request, "we don't have COD for either one of them. If we can't even prove their deaths were murder, it'll be hard to prove they're connected."

"Well it's out there somewhere. It has to be."

Kate pushed open the door, holding it behind her as she stepped onto the sidewalk. "Yeah, well, maybe Lanie will find something."

Hopefully. At this point, it was the most promising scenario.

* * *

"Morning guys," Kate greeted as they entered the bullpen, Castle veering off to the break room while Kate headed to her desk, removed her jacket and booted up her computer.

"Hey, what'd Lanie have to say?" Ryan asked, standing and making his way to the murder board, folders in hand.

"She thinks our vics might've been poisoned," she relayed, snagging a marker and beginning to add to their fairly empty murder board.

"She thinks they're connected?"

"I mean, I think they have to be," Kate agreed. "Let's compare phones and financials, see if we can find anything that might suggest a connection."

"You got it."

While Ryan headed off to gather the necessary information on the two young women, Kate busied herself with retrieving a second white board, re-outlining what they had for Jenna's case. She arranged the boards next to each other, jotting down every piece of information, then standing back to scan the information.

"You know, this might be nothing," Castle began, passing his wife a mug of coffee as he approached, and gesturing to the 'potential subjects' portion of the murder board. "But wasn't Ernesto wearing a Pace University hoodie last night?"

"Yeah, so?"

"So that's where Sara and Jenna met," he recollected accurately.

Kate tilted her head, contemplating.

"We don't have anything better," Castle pointed out around a drink of coffee.

"Hey Espo," Kate called across the bullpen, waited until he looked up from the financial records before continuing. "Let's dig into Ernesto, see if we can come up with anything connecting him to Jenna. Castle and I are gonna go to Annalise's apartment, talk to her coworkers. See what we can find."

"On it, boss," he complied easily.

Kate turned back around to find Castle already holding out her jacket, offered a tender smile before turning her back and allowing him to help her into the garment. He turned her around with a gentle touch on her shoulders, smoothed the collar as she fastened the buttons.

"Thanks," she murmured, grabbing her leather portfolio, phone, and keys before turning again.

She reached out, discretely linked her fingers with his own as she made her way to the elevator, Castle falling into step next to her. He looked shocked at the contact but wasn't about to complain; he merely smiled to himself, careful to keep his eyes focused neutrally ahead of him as they waited for the elevator.

The moment the doors closed, however, it was a very different story.

* * *

_Thoughts?_


	8. Chapter 8

_Author's Note: I want to take a minute to thank all of you for your lovely reviews. They've been very encouraging and have put a lot of smiles on my face! Thank you also to those of you who have passed along some tips - as this is my first time attempting to write a case, I still have a lot to learn. I really appreciate the feedback._

* * *

**Chapter 8**

They really needed to get themselves under control.

The thought looped on repeat through Kate's mind as the elevator doors parted in the lobby of the 12th, revealing a bustling hive of activity, and she silently thanked the powers that be that everyone was too focused on their own work to notice the lingering signs of Castle's kiss and the way he'd pressed her back against the wall as his lips and hands made the most of their short ride to the ground floor.

She strode out of the elevator in front of him, shoving her free hand in her pocket and focusing her eyes straight ahead in an attempt to quell the arousal thrumming through her veins. Her heart was racing, her skin tingling, and when he caught up to her and guided her through the front door with a hand splayed across her lower back, she shivered sharply.

So much for tamping it down, Kate thought self-deprecatingly. They'd worked together for over six years prior to their wedding, two of which included a personal relationship as well as a professional one. So why had marriage seemingly evaporated all of their self-control?

Then again, during the initial honeymoon period she'd been on suspension and they hadn't had to contend with restraining themselves while at work. Hell, they hadn't had to restrain themselves at all. Following the excitement of their newfound engagement, she'd moved to DC, rendering the issue moot. But now that they were here together, still giddy over the rings on each other's fingers and the wonderful memories of the previous two weeks away...

She couldn't help herself.

Not that Castle seemed to mind. No, he seemed to be enjoying it a little too much, if the smug grin upturning the corners of his mouth was any indication.

When they separated so Kate could walk around to the opposite side of the car and he trailed his hand across her ass before returning it to his side, however, she knew she had to put her foot down.

"Castle."

She shot him a glare which he assumed was intended to be menacing; knowing that he was the reason for the lust darkening her eyes rendered it completely ineffective.

"What?"

"Work. Professionalism." she reprimanded.

"You weren't complaining in the elevator."

She slammed her door with much more force than strictly necessary and when she spoke, the words were laced with frustration. "Shut up."

He bit down on his tongue, redirected his focus to removing the pleased smirk from his lips. But nothing could remove from his mind the memory of her lithe, warm body plastered between his chest and the elevator wall, the way her legs very nearly gave out as his teeth scraped gently over her pulse.

It'd been a long time since she'd lost control quite that quickly.

* * *

Annalise and Ernesto's apartment didn't reveal much, and neither did chats with various neighbors. Her coworkers at Unified National Bank uptown were equally clueless as to who'd want to hurt her.

To say that Kate was frustrated was an enormous understatement. She hadn't been ready to come back to work in the first place, and to find herself enmeshed in two cases that seemed to simultaneously be related yet not at all connected, was only adding to her level of irritation.

Not to mention the fact that Castle was wearing a deep purple shirt and hadn't taken the time to shave this morning. He looked deliciously attractive, and the sidelong glances he kept throwing in her direction weren't doing anything to calm her current state.

Hopefully someone else would've uncovered something by the time they got back to the precinct. The sooner they could close these cases, the better.

* * *

As luck would have it, Esposito had come through.

"So I did some digging." he held up a file folder, passed it to Kate as she approached his desk. "Turns out our boy Ernesto was involved in a car accident about three years ago."

She opened the folder and Castle stepped up behind her to read over her shoulder. She knew it was harmless, that he was focused on the case, but the way her body was reacting to the play of each breath across her skin was very much not innocent.

"What happened?" she asked as she scanned the report.

"He was in the passenger seat when another driver ran a red, t-boned their car. He and the driver were fine but the passenger in the back seat and the driver of the other car didn't make it."

"I take it there's more to the story," Castle queried.

"Turns out, the driver of the car was Ernesto's girlfriend at the time." Espo reached out to flip up the first page, revealing the rest of the details as well as pictures from the scene.

"Sara?"

"Was she charged?" Kate asked.

Espo shook his head. "She'd had a couple drinks earlier that night but her BAC was below the minimum. And she had the right of way, so..." he let the rest of the sentence trail off.

"So Sara's roommate-slash-best friend and her ex-boyfriend's current girlfriend both die seemingly inexplicably within two days of each other?" Castle narrated skeptically.

Kate raised an eyebrow. "Guess it's time to go pay her another visit."

* * *

When the door to 8E opened, it was a ghost of the woman they'd recently met who looked up at them. Her eyes were red-rimmed, hair tossed up in a knotted bun, and she looked as though she hadn't slept in days.

"Detective," she greeted, wiping her eyes as though suddenly self-conscious.

Castle offered what he hoped was a compassionate smile while Kate opened her mouth to speak. "Mind if we come in for a few minutes?"

Sara stepped back, shutting the door behind them before gesturing to the sofa. The young woman sank into the armchair, glancing around uncertainly. "Um, what can I do for you?"

Kate leaned forward, placed a picture of Annalise on the coffee table in front of Sara. "Do you know this woman?"

She shook her head. "No. Who is she?"

"How about him?" She extracted a photo of Ernesto, set it next to the first.

"Ernesto," she breathed, a combination of concern and disdain. Her head snapped up. "Is he okay?"

"He's fine," Kate answered. "However, his current girlfriend isn't."

Sara pointed to the other picture. "This girl?"

"She's dead," Castle said by way of an answer.

"Dead?"

"Just like Jenna."

Sara narrowed her eyes. "What are you saying?"

"I just find it odd that your roommate and your ex's current girlfriend were both found dead," Kate spelled out.

"You think _I_ killed Jenna?" Sara exclaimed in shock. "She was my best friend. Why would I kill her?"

"Any number of reasons," Castle began, holding up his fingers poised to being ticking off each bullet point. "Jealousy, anger..."

"She was my best friend," Sara repeated angrily.

"And Ernesto's girlfriend?"

"Please," she huffed. "We broke up three years ago. He can date whoever he wants."

"Technically that would be whomever..."

"Castle," Kate interrupted with a hand on his arm. She turned back to Sara. "That doesn't sound like the voice of someone who's gotten over the breakup."

She shook her head. "Look, it was rough, okay? I was going through some stuff and Ernesto – he wasn't very supportive. But that doesn't mean I killed his girlfriend."

"In that case, you won't mind me asking where you were yesterday between 4 and 6 p.m.," Kate rattled off.

"At work. I'm a waitress at Casa La Femme in the Village."

Kate jotted it down before switching gears. "We'll be sure to check that out. In the meantime, can you think of anyone in Jenna's life who would've wanted to hurt her? Maybe a boyfriend or a coworker?"

Sara shook her head. "She didn't have a boyfriend. But, I mean, maybe her ex," she suggested.

"Bad breakup?"

"He took it pretty hard," she recalled. "Their relationship got serious really fast."

"I take it Jenna wasn't okay with that," Castle offered.

Sara shook her head. "They'd been together four months when he started talking about marriage. She freaked, told him she didn't want to see him anymore."

"And this happened recently?" Kate questioned.

"About three months ago," Sara answered.

"Any problems since then?" she asked. "Did he ever come looking for her?"

She shrugged. "Not that I know of."

"Was she seeing anybody else?"

"She went out to dinner with some guy a couple of weeks ago, but I think it was just a one-time thing."

"Can you think of anything connecting her to Ernesto or his girlfriend?" Castle jumped in. "Did she know him?"

Sara shook her head. "No. I mean, she knew _of _him. But I met Jenna after we broke up."

Kate nodded thoughtfully, collected the photos and stashed them back in her portfolio. "Okay, thank you."

"So you think she was murdered?" Sara asked shakily as Kate and Castle got to their feet.

"We're not sure yet," she answered honestly. "But we're examining every possibility."

Sara nodded to herself, almost trance-like, eyes staring unseeingly at the coffee table even as they offered a gentle goodbye and let themselves out of the apartment.

The moment they were out of earshot, Castle spoke. "You believe her."

She turned her head, brow furrowed in confusion. "You don't?"

"She's faking it."

"She's devastated," Kate countered

He scoffed.

"Castle."

"Come on. She and Ernesto are the only connections between the two vics, and his alibi checked out for both murders. It _has_ to be her."

"We'll have unis go to Sara's work and talk to her friends, verify her alibi for both deaths," Kate explained. "But I don't think it's her, Castle."

"Remember those words you said yesterday, De_tec_tive?" he asked, accentuating her title in far too sexy a manner.

She raised a doubtful eyebrow.

"That I was right," he clarified proudly, before adding under his breath. "Like always."

She rolled her eyes.

"You know, you're stuck with me now," he gloated. "For the rest of your life. The sooner you accept it, the better."

Kate snorted.

Yeah. Right. Never gonna happen.

What had she gotten herself into?

* * *

_Thoughts?_


	9. Chapter 9

_Author's Note: After all the research I've done for this fic, I understand why Castle knows so many random facts. Along those lines, while I do have a science background, it's not in the medical field - if there are any mistakes, I apologize. Please feel free to correct me._

* * *

**Chapter 9**

He was wrong. A fact which Kate was all too eager to point out, much to Castle's chagrin.

"Seriously?" he questioned emphatically.

"Her alibi's solid bro," Esposito answered. "Sorry."

"It has to be her," he protested. "There aren't any other connections between our vics."

Kate's phone vibrated against the surface of her desk and she retrieved the device, glanced at the screen before automatically reaching for her jacket.

"Lanie," she offered by way of explanation. "She's got something."

* * *

Kate hastened through the door of the morgue, Castle on her heels, caught up in spinning an elaborate tale of lust and jealousy and betrayal that she assumed was somehow meant to disprove Sara's alibi. She wasn't entirely sure. She'd stopped listening a couple minutes back.

"Hey, Lanie. You found something?"

"Cause of death for your second vic." The ME crossed the room as she spoke, collected a folder from her desk. "She was poisoned."

"By what?"

"I collaborated with a couple colleagues of mine from poison control and found compounds consistent with the metabolism of aconite. It's a highly poisonous compound from..."

"Oh, Wolfsbane!" Castle exclaimed. "Right? It's used for pain relief. I researched it once for when Derrick Storm was on a mission in China but I didn't end up using it because..." he abruptly became aware of two sets of eyes fixed on him, trailed off. "Right. Sorry." He nodded to Lanie. "Continue."

"As I was saying," the ME began again, "it's a plant-derived toxin that's also occasionally used as an analgesic. However, its use is uncommon, because ingestion of more than a small amount can be fatal."

"You think she was dosed?"

"According to her medical records, there doesn't seem to be any reason for her to be taking it. Not to mention that it's not commonly prescribed, especially in the US."

"So where would our killer have gotten this?" Kate asked.

"Well, that's hard to say," Lanie began. "Because of its toxicity, it's highly regulated. However, the plant is native to parts of the northern hemisphere, particularly mountainous regions. Anyone with knowledge of plants and a thorough understanding of chemistry could've picked some and extracted the poison."

"And how would it have gotten to Annalise?" Kate questioned.

"I'm guessing it was mixed in with her beer," she answered.

"How nefarious," Castle commented.

"Yes, and fatal," Lanie reminded him. "And," she continued, gesturing with one gloved hand, "I did some research. Initial symptoms include nausea and vomiting, and death presents signs of cardiac and respiratory failure."

"Just like Annalise."

"Mmhmm."

Silence fell as they contemplated this new information, before Kate raised a valid point. "What about Jenna?"

Lanie shook her head. "Test came back negative. I'll run it again just to be sure, but if Jenna was poisoned, it looks like our killer used something different."

"Okay, thanks." Kate turned to go, paused and whirled back around. "Oh, uh, anything else that might connect our two vics."

"I compared their medical records, hospital visits, even places of birth, but there aren't any similarities," Lanie reported. "However, Jenna's medical records aren't complete. There're four years missing."

Castle turned to Kate, index finger extended as he gestured at her. "Didn't Sara mention Jenna lived abroad for four years?"

"Yeah, in South America, though she didn't say where." Kate turned back around to Lanie. "I'll talk to her parents, see if we can get ahold of those. Might give us some insight."

* * *

Jenna's parents consented to email the missing medical records which, due to frequent travels, were all already in electronic form. No sooner had Kate hung up the phone than a message appeared in her inbox, a selection of files attached. She opened the first document, scanned it briefly before forwarding the entire message to Lanie. With any luck, it would shed some light.

"Ready to head out?" she asked as she shut down her computer. They'd arrived back at the bullpen just ten minutes ago, and Kate hadn't even bothered taking off her coat. It'd been a long few days and there wasn't a lot more they could do tonight anyway.

When she received no answer, she finally looked up, sought out her husband who was intently focused on the case once again, lips moving slightly as he synthesized the facts at hand with the story that was inevitably forming in his mind. With an adoring shake of her head, Kate tucked the case files under her arm, grabbed their empty coffee mugs, and headed to the break room to rinse them out. She followed up by storing away the case files, stopped to talk to Ryan and Espo on her way back to her desk, giving Castle plenty of time to work through his latest stream of thoughts.

"You onto something?" she asked a few minutes later, coming to stand next to him and nudging his elbow with her own.

"Just trying to figure out the connection," he answered, eyes still glued to the boards.

"Mmmm, yeah," she commiserated.

"Her parents didn't know Annalise?" Castle asked.

Kate shook her head. "Nope. They did have the medical records though. Lanie's gonna take a look at them and let us know."

Castle hummed an answer, clearly preoccupied.

"What?"

"It just doesn't make sense," he muttered, almost to himself. "One vic killed by someone slipping poison into her food, the other potentially poisoned with something... Wait. Poison in her food." Castle echoed his own words, turned excitedly to Kate. "Where's the file on Jenna?"

She opened her mouth, poised to speak, but before she could so much as find the words he was already dashing across the bullpen in a hurry, seemingly not in need of her answer after all.

Okay then.

Apparently they weren't leaving quite yet.

* * *

"Everything okay?" Kate asked, passing her husband a glass of red wine before curling onto the sofa next to him. Whatever he'd been onto prior to leaving the precinct, he still refused to divulge more than the fact that he'd had a hunch, and after a few minutes, Kate had simply given up. If it panned out, she'd find out eventually and if not, then it didn't really matter in the end. What mattered was that they found the killer, brought him or her to justice.

But in the meantime, there were more pressing issues at hand.

"Yeah. Why?" Castle answered, searching her eyes.

"I know this case has been tough on you," she murmured.

"No, it's, I mean, yeah. I just can't imagine what their parents must be going through. They had their whole lives ahead of them, and then..." he released a heavy exhale, tilted his head back against the cushions.

"We're gonna figure this out, Castle," she assured him.

"But that doesn't bring them back."

Kate sighed emptily. "No. No it doesn't."

"Sometimes I wish Alexis was still a little girl and I could wrap her up in my arms and protect her from the world," he lamented.

Kate set her glass aside, turned to face him more fully. "Rick," she called softly. When he barely acknowledged her voice, she reached out to cradle his free hand in her own, thumbs tracing gentle lines across the back of his palms. "I know you worry, but this job? This kind of thing? It doesn't happen every day, and it doesn't happen to most people."

"I know, but..."

"Please, Castle," she pleaded. It was times like this that she hated how shadowing her had destroyed his innocence. It was still there. She still saw it at times. But it wasn't the same. He carried these burdens now, too. Burdens he should never have to bear. "It's okay to worry, but please don't let this swallow you up."

He nodded, more to himself than to her, but didn't speak.

"We can make an appointment for Alexis, okay? Just to be safe. Have them run some tests."

He nodded absently but it was a long moment before he broke the silence. "I don't know how you do it."

"I have you by my side," she answered in a low, soothing tone. "I have you to help push away the darkness." She squeezed his hand. "And we have this to come home to."

"But what if...?"

"Don't." Her voice was stronger now, an emphatic appeal. "Don't, Castle."

"She's almost twenty one," he answered, still caught up.

"I know," Kate placated. "But she's a smart girl, Castle. And I can talk to her if you'd like. Give her some advice on what to look for, how to stay safe."

Castle lifted his head. "You'd do that?"

She shrugged as though it wasn't a big deal. "Of course. She's family."

His lips parted, poised to speak, and Kate searched his eyes, raising an eyebrow and leaning her head forward encouragingly as she awaited his words.

He squeezed his lips together, eyes finding hers as he spoke. "You never stop amazing me, you know that?"

Kate dipped her head shyly but couldn't suppress the grin that spread across her face. Castle and his beautiful words.

She worried her lip with her teeth, blinked slowly before flicking her gaze up to his, bright blue and penetrating. "I love you too."

* * *

_Thoughts?_


	10. Chapter 10

**Chapter 10**

The tender silence was promptly interrupted by a key in the door, and Castle and Kate's heads automatically swiveled towards the source of the sound. The lock clicked, followed by the turning of the doorknob, and the door opened to reveal a swirl of long red hair as a young woman stepped across the threshold, shutting the door behind her.

"Alexis?"

His daughter smiled, dropping her purse onto the floor and unbuttoning her black and grey plaid pea coat. She wore heeled black boots over form-fitting dark wash jeans, and a deep green sweater that beautifully complemented the color of her hair.

"Hey."

"Everything okay?"

She shrugged, draped her jacket over the arm of the sofa. "You seemed upset the other day and I just thought..."

Castle stood without preamble as Alexis approached, wrapped her up in a crushing hug, and he could feel a weight lift from his shoulders, some of the anxiety of recent days rolling off of him.

"Are you sure you're okay?" Alexis asked as he loosened his grip, perceptive eyes searching his face.

"You would tell me if something was wrong, right? If you were in trouble or out drinking and..."

"Dad..."

"Or if someone..."

"Dad," she interrupted more firmly. "I'm only twenty, remember?"

"I know, but..."

She stepped back, folded her arms defiantly. "Is this about the case?"

Castle opened his mouth to reply, closed it again when no words escaped.

"Whatever happened...that's not me," his daughter iterated. "I'm careful."

"I'm sure they thought they were being careful too," he voiced. "And now they're dead."

"Dad..."

"Castle," Kate murmured in his ear, resting a gentle hand on his shoulder as she stepped up behind him. He startled slightly, hadn't even heard her approach. "Could you give us a minute?"

He took a moment to compose himself before nodding, backing away and leaving them alone to chat. "Right, of course."

Kate waited until he'd crossed to his office, disappeared from view, before sinking into the sofa and gesturing for Alexis to make herself comfortable.

"Is Dad okay?" the girl asked worriedly.

Kate sighed. "The case we're working right now – the victims are two girls not much older than you."

"That's awful. What happened?"

"Well we're still figuring that out," she relayed. "But they presumably got tied up in something. Something bad."

"And Dad's worried I might end up in the same situation?" she profiled accurately, stubbornly crossing her arms over her chest. "Because he doesn't trust me."

"No, Alexis, he trusts you," Kate promised. Things had been rocky for a while but over the last few months they'd managed to repair most of the damage, resuming their original close relationship. Nevertheless, Castle's overprotective tendencies were not to be quashed, nor was Alexis's ever-growing independence. It was a battle that neither was destined to win. "But things happen, sometimes unintentionally. And you're a beautiful, intelligent young woman."

"Yeah but..."

"I know you know how to stand up for yourself," Kate continued, holding up a hand to prevent a protest. "And I know you have a solid head on your shoulders. But he's your dad, Alexis, and he has a writer's imagination." Alexis rolled her eyes knowingly. "He's always gonna worry, and there are times where he'll be annoyingly protective. My dad was the same way when I was younger."

"So what am I supposed to do?"

"Keep your head on straight and always be aware of what's going on around you," Kate suggested. "Surround yourself with people who are the same. And just remember that he means well. And he loves you."

Alexis seemed to relax at that, relenting a bit of her stubborn defiance. "I know."

The conversation dissolved into a variety of other topics from there, Kate asking about school, Alexis animatedly relaying a story from one of her classes and recounting an interesting guest lecture she'd attended the previous evening.

As their easy back-and-forth came to a natural pause a few minutes later, Alexis stood, shifted to straighten her sweater.

Kate nodded in the direction of the office. "You should go talk to him."

Alexis offered an assenting smile. "I will. Thanks, Kate."

She shrugged as though it wasn't a big deal. After all, Castle was her husband, and though she wasn't much of a mother figure, Alexis was technically her step-daughter. They were family. "Not a problem."

"No really," the girl pressed. "I'm glad he has you."

Kate smiled broadly, heart overflowing with love. "I'm lucky to have him too, Alexis."

* * *

"So I ran some more tests, like you suggested," Lanie offered first thing the next morning as they strode into the morgue, coffee cups in hand.

Kate furrowed her brow in confusion. "I didn't sugge..."

"Not you." She nodded to Kate, then to Castle. "Him. And I think he might be onto something."

Ah. That explained what he'd been up to yesterday.

Castle grinned smugly. "See, I told you..."

Lanie held up a hand, halting his proud declaration. "Let me finish. I ran a variety of blood tests, and this time something popped." She opened a folder, passed it to Beckett. "I found higher than normal levels of IgE. It wasn't a lot, but it was enough to raise a red flag."

"IgE?" Kate repeated, brow furrowed.

"It's a type of antibody. Part of the body's immune response," Lanie explained. "It's typically elevated in people with allergies, particularly following an allergic reaction."

Kate dipped her head in confusion. "You think she had an allergy attack?"

"This along with the low blood pressure and edema around her airways," Lanie listed. "My guess is that your vic went into anaphylactic shock."

"And what could have triggered that?"

"Medication, insect stings..."

"I doubt she was stung by an insect at the bar," Castle interrupted.

"Food allergies," Lanie continued with a nod in Castle's direction.

"So her death could have been accidental?" Kate asked.

"I ran some additional tests just to be sure," Lanie continued. "Along with the vodka martinis she'd been drinking, it appears she'd also ingested small amounts of peanut oil."

Kate furrowed her brow. "That's not an ingredient in any martini I've ever heard of."

"Not to mention an odd method of consuming peanut oil," Castle mused.

Lanie nodded in agreement. "I checked it against those missing medical records you sent me. She was diagnosed with a peanut allergy at age eleven, after a severe reaction landed her in a hospital in Peru."

"So you think she _was_ murdered?" Kate pieced together.

"I think that's the most likely scenario."

"So someone doses her drink with peanut oil," Castle began. "Enough to set off the reaction but not enough for her to taste it."

Kate took a step closer. "After a few minutes, she realizes what's happening..."

"And that's when she panics and runs out," Castle recollected.

"Mmm, someone with a food allergy would've had an Epipen," Lanie interrupted.

"Maybe she didn't have one with her," Castle suggested.

"No, Lanie's right. She wouldn't have gone out without one," Kate mused.

"Maybe she couldn't find it."

"Then why not call 911?"

He shrugged. "Maybe she panicked."

"Or maybe," Kate began, advancing one more step, eyes lighting up as the pieces fell together in her mind, "she _did _have one when she left the house, but..."

"Her stolen purse!" they exclaimed in unison.

Kate's eyes eagerly searched her partner's face, found his eyes twinkling back at her, that familiar spark of excitement from their crime-solving banter.

Lanie crossed her arms over her chest, cleared her throat pointedly, and the partners jerked apart, hastily putting some space between them.

Kate snuck a glance at her friend, found Lanie regarding them with a raised eyebrow, her lips curved into an amused smile. The detective stepped back, pressing her lips together in embarrassment.

"Shut up."

* * *

_Thoughts?_


	11. Chapter 11

**Chapter 11**

"So," Castle offered, breaking the silence as they exited the morgue. "What are the odds that her purse, containing her Epipen, was stolen immediately prior to her having an allergic reaction?"

"Obviously our thief knew it was there," Kate agreed.

"Exactly."

"Which means they had to have known about her allergies."

"Right."

"So someone who knew her. Well."

"The roommate?" Castle suggested.

"Her alibi was solid," she reminded him.

"For the other murder. But she was right there with Jenna at the bar. How hard would it have been for her to slip some peanut oil into Jenna's drink when she wasn't looking?"

"So now you're saying the murders aren't connected?" Kate asked, face adorably screwed up in confusion.

"No, I still think they are."

"So Sara has a partner?"

"It's possible."

"But who?"

"The ex-boyfriend?" Castle postulated.

She recalled Sara's reaction to his picture. "I didn't get the feeling that they were particularly on speaking terms."

"Or maybe that's what she wanted us to think."

"Okay, assuming they're in it together, what's the motive?"

"I..." Castle began, trailing off when he came up empty. "No clue."

"Mmmm."

They exited out onto the street then, Kate in front of Castle as they stepped through the door. Manhattan was teeming with life this early in the morning, people jostling to and fro, horns honking, everyone in a hurry to arrive at their destination. A middle-aged man hustled past, bumping into a young woman, and she stumbled to the side, nearly dropped her briefcase. Castle paused, allowing her space to regroup before reaching for Kate. She twined her hand with his, allowed him to tug her out onto the bustling sidewalk. They expertly wove their way through the fast-moving throngs of people, separating only once they'd reached her cruiser.

The morning sun shone brightly down on the windshield as they opened the doors, slid into the car next to each other. The doors shut in unison as they settled in, reached for their seatbelts, and Kate couldn't help but smile at the synchronicity of their movements.

"Maybe it all comes back to the accident," Castle posited as they pulled out into traffic, joining the flood of slow-moving cars.

She forced herself to refocus on the case. "The car wreck?"

"We know Sara and Ernesto were both involved in it," he pointed out.

"But Jenna and Annalise weren't."

"Mmmm, true," Castle conceded. He shook his head, face scrunching up in frustration. "What is it with this case and nothing making sense?"

Kate hummed in agreement as they proceeded through the next intersection before promptly coming to a stand-still once again. Stuck in endless traffic at nine o'clock in the morning. It was lining up to be another long day.

* * *

"Huh."

Kate swiveled around in her chair, pen in one hand, the implement twirling around between her nimble fingers. "What?"

"Just looking at the accident report from three years ago," he explained.

"And?"

"The girl who was in the back seat – the one who died. It looks like she was a friend of Sara's from school." Castle passed Kate the report. "Carly Mathers. Twenty one at the time. Died at the scene from blunt force trauma when the other car slammed into the rear passenger side of Sara's car."

"What else do we know about her?" she asked, skimming the lines of text.

"Well, statements from Sara and Ernesto say that they were friends from Pace and that they'd been out at a bar. Ernesto and Carly were both fairly intoxicated, but Sara's BAC was below the legal limit."

"But none of this explains Jenna and Annalise's murders," Kate pointed out.

"Maybe they were involved somehow?" he suggested.

"How? There wasn't anyone else in the car, and the driver of the other car died as well."

"Were they there that night?"

Kate shook her head. "Sara said Jenna didn't know Ernesto."

"Maybe she was lying."

She shrugged. "Ryan is with CSU having them check Sara and Jenna's apartment and the bar for any indication of peanut oil. And Espo is verifying her alibi for Jenna's murder. But I really just don't think she was involved."

Castle fell silent then, turned his attention back to the murder board while Kate took her time reading through the accident report, coalescing the information there with everything else they'd learned about their victims and potential suspects. It didn't seem related, but they didn't have a lot else to go on. She pressed her lips together in frustration, shook her head. None of this made any sense.

She reached for her coffee mug, huffed in frustration upon finding it empty. Kate rose, collecting Castle's empty mug as well, but she paused before making her way to the break room, arrested by the look in Castle's eyes. She knew that look.

"You onto something?"

He turned, head tilting back to look up at her from his chair. "Just wondering why our killer didn't use the same poison on both of them."

"Well, Annalise wasn't allergic to anything," Kate pointed out.

"But why go to the trouble to get the – whatever its fancy name is..."

"Aconite."

"Right. Why not use that on them both?"

"Allergy attack looks more accidental," she offered with a shrug. "But that wouldn't have worked on Annalise so our killer had to pick something different."

He half-nodded in acquiescence. "I guess." It was true. Someone had put a lot of thought into making these deaths look accidental, simple tragedies to cover up the murders.

"Well," Kate stated purposefully. "If we ever find our killer, we can ask him." She gestured towards him with his mug. "Coffee?"

He offered her a tender smile, confusion in his eyes fading away the moment they met hers. "Thanks."

* * *

When Kate returned to her desk, Ryan and Esposito had joined Castle at the murder board, and the three men were standing in a semi-circle, tossing ideas back and forth.

"Anything?" she asked, passing Castle a steaming mug of coffee.

"No one at the bar remembers seeing anything out of the ordinary," Espo offered. "But it was crowded. It would've been easy for our killer to dose her drink and sneak away unnoticed."

"So it could've been Sara," Castle chimed in.

He shrugged. "It could've been anyone in the bar, bro. There aren't any security cams. Hell, we don't even have a way to track down patrons unless they paid by credit card. I don't think we're gonna be able to narrow this one down."

"No signs of peanut oil?"

"Bar doesn't stock it and there's not any lying around."

"And nothing at Sara and Jenna's place," Ryan offered. "In fact, there was a complete lack of any type of nut-containing product."

"What about Jenna's ex-boyfriend?" Castle piped up.

"I was able to track him down from her phone records," Esposito explained, sticking a picture up on the murder board as he spoke. "James Knowlton. Twenty eight. Former salesman at an outdoors store in Brooklyn."

"Former?"

"Turns out he packed up and moved to Saratoga about a month ago. Guess he wanted a fresh start."

"Any chance he was back in the city recently?"

Espo shook his head. "Nope, his alibi is solid."

"Okay, well what about her neighbor?" Castle theorized, grasping for anything they might've overlooked.

"The one who found the body, you mean?"

"He said he didn't even recognize her," Ryan recalled.

"Don't you find that odd, though?"

"Bro, this is New York," Esposito defended. "How many people could pull their neighbors out of a lineup?"

"Pretty young girl like her living right up the stairs? Trust me," Castle announced. "He'd recognize her."

Ryan raised an eyebrow. "You seem pretty sure of yourself."

Esposito crossed his arms in intrigue, and even Kate turned to face him. Castle held up his hands in surrender. "I'm just saying from past experience, she was the kind of girl a guy would remember."

"Past experience, huh?" Esposito teased.

"Please," Castle scoffed, looping his arm around Kate's shoulders in spite of their location.

"Castle," she hissed, ducking out from under his arm. She didn't get far, though, frozen in place by his next words and the sincere look in his piercing blue eyes.

"We all know the prettiest girl in the building lives with me."

Kate just stood there, feet rooted to the floor. Heat flushed her cheeks as his words washed over her, and she quickly became aware of the stares of her coworkers, the knowing smirks curling up the corners of their mouths.

"Right, uh, okay," she stammered, pausing for a long sip of coffee, buying time to regain her bearings. He couldn't keep saying things like that in public places. It made her want to do things to him. Things that were most certainly _not_ appropriate for said public places.

She still had the fading remains of a love bite on the inside of her left thigh from the last night of their honeymoon, another beneath her right breast. A jolt of arousal rippled through her at the thought of his teeth on her skin and Kate bit down hard on her lower lip, forced the memory away. How was she ever supposed to solve this case when she couldn't stop picturing herself naked and writhing beneath an equally naked Castle?

"Beckett?" Ryan asked tentatively.

Right. Murder case.

"Let's, uh, start concentrating on Annalise's murder more closely," she managed. "If we can find her killer, maybe we can tie him or her back to Jenna. You guys dig into her life, Castle and I are gonna head back to the restaurant, see if we can churn anything up."

"You got it, boss," Ryan promised cheerfully, eyes still twinkling merrily.

"And let's, uh, interrogate the neighbor. Just to be sure," she called after Ryan and Esposito's retreating forms.

"Okay, here's what I don't get," Castle began as he set aside his coffee mug to help Kate into her jacket. She shivered as his fingertips trailed over her biceps, bit her lip to suppress it. While she did up her buttons, Castle paused to grab his own coat, arms easily sliding through the sleeves before following his wife to the elevator. "Slipping something into Jenna's drink at a crowded bar – easy to get away with. Poisoning someone's food at a restaurant – little more difficult."

"It's a sports bar, not a sit-down place," she reminded him. "And there was a game on. People would've been otherwise occupied."

"But still, it would've been a lot more difficult to go unnoticed. Unless..."

She pressed the button for the elevator, turned to face her husband. "Unless what?"

"Our killer works there."

The doors slid open in front of them and they stepped in side by side. "Guess it's time to go find out."

* * *

_Thoughts?_


	12. Chapter 12

**Chapter 12**

"How's Alexis doing?"

He shrugged. "She's fine. Doesn't seem at all worried about anything I said last night."

"Castle, she's a smart girl," Kate soothed. "You know that."

"But Paris..."

"Was about something entirely out of her control," she interrupted. "Nothing she could've done would've prevented that. But she was smart, Castle. Resourceful."

He ran a hand over his face, sighed heavily. "I know."

"I talked to her," Kate reminded him.

"I know," he breathed. "And I really appreciate that. But..."

She held up a hand. "No buts. You can't protect her from everything. No one can. The best you can do is to teach her to be alert and aware of her surroundings. To stay calm in the face of a crisis." She extended an arm across the console, rested her hand on his leg. "And you've done that."

"How'd you get to be so smart?"

"You forget that I used to be a teenage girl," she offered wryly.

He threw her a lopsided smile, covered her hand with his own on his leg. "You're gonna be one hell of a good mom one day, you know that?"

She trapped her lower lip between her teeth, glanced over at him shyly, silently hoping that when the day came, she'd live up to all of his expectations.

* * *

Kate's phone rang just as they were leaving the restaurant and she paused on the sidewalk to take the call and pass along what they'd found. Which wasn't much. They'd spoken with the manager and some of the staff but most of them hadn't been working that night and none of them claimed to recognize either Annalise or Jenna. They'd do some more digging but in the meantime, they didn't have much to show for their trip.

"CSU report just came back on Jenna's purse," she relayed to Castle as she ended the call from Ryan, pocketed her phone.

"Anything?" he asked as they headed off down the street.

"Nope. Killer must've worn gloves."

He sighed. "Still no leads."

"Well, we'll run background checks on everyone from the restaurant, go through traffic cam footage from outside. And CSU is searching for any traces of the poison. With any luck, we'll come up with something."

* * *

"So what do we do in the meantime?" Castle asked, leaning back against her desk as Kate came to rest next to him. They'd grabbed take-out on the way back to the precinct, taking a much-deserved lunch break in the break room. Even so, CSU reports wouldn't be back for at least a couple of hours, and unis were running background checks, but that too would take some time.

Kate shrugged one shoulder. "Keep digging, see what we can find."

She crossed one arm across her chest, other arm bent at the elbow but remaining vertical, chin coming to rest on her fisted hand. Her brow was furrowed in concentration, lips moving ever so slightly as she silently talked through the facts of the case.

"What are you thinking?" Castle probed after a while.

"Just going over the timeline of Jenna's final minutes."

"Something doesn't add up?" he presumed.

"Just – her reaction to it all. I mean, why not have the bartender call 911?"

"Maybe she didn't think they'd get there soon enough." Castle explained.

"So she decides to go upstairs?"

"She probably had another Epipen in her apartment."

"But her keys were in her missing purse," Kate pointed out.

Castle paused, considered. "Maybe they'd left the door unlocked?"

"Mmm, it was locked when CSU got there."

"Then why not try to find Sara?"

"It sounded like she did. When she ran out of the bar."

"By which point she was already gone," Castle pieced together.

"Don't you find that strange, though?" Kate queried.

"What?"

"How long does it take to ask the bartender 'have you seen a purse?'"

Castle shrugged. "Not very, assuming she didn't have to wait to get his attention."

"Exactly. How far could Sara possibly have gone in that time? Especially in a crowded bar?"

"You think she intentionally hurried away?"

"I think she was _hurried_ away," Kate clarified. "But not necessarily of her own volition."

"You mean by her friends?"

"When I talked to her, she made it sound like she was wanting to stay but her friends were tugging her towards the door," she recounted.

"Like they wanted to get her out of there as fast as possible?"

"Exactly. I mean, think about it. Jenna buys the drink, her purse goes missing, she starts having an allergic reaction, and her roommate just happens to run into some friends who promptly whisk her away. All in under fifteen minutes."

"So one of these 'friends,'" he curled his fingers in air quotes, "steals Jenna's purse and slips peanut oil into her drink, then promptly 'runs into' Sara."

"And immediately invites her to a different bar, because if she's around, she might recognize what's happening."

"And help Jenna."

"Exactly."

"That's our killer."

Castle's wide, darkened eyes sought Kate's as they spoke, so drawn in by the story they'd spun. It'd been more than six years now and they'd only grown more in sync as time passed.

She gazed back at him with that familiar spark of attraction and lust and something much deeper. He was helpless against it, captivated by the look in her eyes and more than a little turned on by their fiery back-and-forth, the thing that had served as their foreplay for nearly four years.

In some ways, it still did.

Their gazes locked. The air in the room stilled, the space between them so fraught with tension as they unsuccessfully fought the magnetic pull luring them together. Kate tilted closer, eyes dropping to his mouth as hers fell open just slightly, her tongue peeking out to wet her lips. Castle leaned in, eyes so dark with passion and desire and...

Across the bullpen a phone rang, and they jerked apart, embarrassed.

"Right, uh..."

Castle pushed his hands into his pockets, took two large steps away from his wife and turned back to the murder board. Kate did the same, eyes flitting back and forth over the information as she grasped for something, _anything_ to say.

Thankfully Castle came to her rescue, spoke the words she'd been trying so desperately to find. "We need to track down Sara's friends."

* * *

Castle headed home a few minutes later when Kate received a text from Lanie, summoning her to the morgue. At first, she assumed the ME had found something to indicate a connection between the two victims. Perhaps something on the bodies left behind by the killer. Until the second part of the message came in.

_Just you. No Castle_.

Kate shook her head. Her friend must've been taking subtlety lessons from Castle.

"What?"

"Lanie wants to see me," she answered.

He glanced at the phone then over to her, taking in the shyness of her features, the way she didn't quite meet his eyes. "I take it this isn't about the case."

Her silence spoke to the correctness of his assumption.

Castle stood, helped her into her jacket, fingers trailing gently over her wrist as he dropped his hands. Kate smiled up at him as he stepped back, so genuine and lovely, lowered her voice so only he could hear.

"See you at home."

Castle smiled back, eyes twinkling. "Don't forget to tell her about the time we..."

Kate clapped her hand over his mouth, eyes narrowed dangerously. "Shut _up_."

His only response was a sexy, suggestive grin.

* * *

"So," Lanie drawled as soon as Kate stepped through the doors of the morgue. She was perched on one of the steel tables, legs swinging back and forth, eyes regarding her friend eagerly.

Kate raised an eyebrow.

"Details, girlfriend. And don't you dare leave out the juicy parts."

"It was a honeymoon, Lanie," she answered, hopping up onto the table next to the ME. "It went pretty much like you'd expect."

"Which is why you don't want to give it up?"

Kate narrowed her eyes.

"Please," Lanie scoffed. "Like the whole world can't tell _exactly_ what's been happening every morning before you show up for work."

Her glare intensified.

"I think we all know that if I hadn't called you the other day..."

"Awful timing, by the way. We still haven't...you know..."

Lanie folded her arms sassily. Kate shook her head. Sometimes her friend was too perceptive for her own good.

"This is exhausting," she admitted.

"The case?"

"Being married."

"Too much sex, not enough sleep?" Lanie teased.

She laughed, couldn't help herself. What she wouldn't give to have the energy to have too much sex with Castle right now.

"Too much case and not enough sleep," Kate corrected. "Or sex."

"I'm having trouble believing you two sleep at all when you're in bed together."

"Lanie."

"I'm just saying..."

"It's just – with this case and the two girls being close to Alexis' age..."

"He's taking it hard."

She nodded. "Yeah, though he's starting to calm down a bit now that he's talked to Alexis. But none of the evidence is adding up, which is just making it more and more frustrating. And we were both jet-lagged, and tired. And we keep getting interrupted." She shot her friend a pointed look.

"You said you wanted to know if I found anything," Lanie defended.

"Yes, well, preferably _after_ eight in the morning."

She raised an eyebrow. "Duly noted." When silence fell, she continued. "Alright, well, I better let you get home. I'm sure you have – other plans – for your evening."

"Lanie."

She held up her hands in surrender. "I'm just saying. You look good, Kate. You both do. And I'm happy for you two."

She couldn't stop the broad smile that split her face, affirming her friend's sentiment. She was happy for them too.

* * *

_Thoughts?_


	13. Chapter 13

_Author's Note: I feel like I can never say this enough - thank you all so much for your lovely reviews/favorites/comments and for sharing the links on tumblr and twitter. I appreciate your support so much!_

* * *

**Chapter 13**

Dinner was delicious, as was the bottle of wine they cracked open with it, one glass with their meal, a second immediately afterward. They settled onto the sofa shoulder to shoulder, clinked their wine glasses lovingly before taking a sip. But without the distraction of cooking dinner, idle chit chat over the hot meal, she could tell Castle's mind was wrapped up in the case once again.

Kate nudged his side gently. He startled, turned to her with questioning eyes.

"You seem a little lost," she offered by way of explanation.

"Just thinking about the case."

She hummed a reply.

When ten minutes passed and he hadn't so much as spoken a word, she finally asserted herself. "Castle, please, can we just drop it for the night."

"Sorry, this case, it's just..." he sighed heavily, trailed off.

"I know, I'm frustrated too," she agreed. "But for tonight, let's just be us, okay? And tomorrow morning, we can head in early and get back to work. Track down Sara's friends and see what they know."

He nodded absently; she was pretty sure he wasn't really even listening. A pained, disappointed sigh was his only response.

"Hey, you okay?"

Castle shook his head, shrugged.

"It's more than just the case, isn't it?" she mused, things beginning to fall into place.

He sighed again, nodded reluctantly.

"Alexis?"

A shake of his head.

"What is it, Castle?" Kate probed gently.

He released a long exhale, buying himself time before finally speaking. "I just wanted to prove that we could do this."

Her forehead creased in confusion. "Do what?"

"Be married and keep solving cases. I love that part of our life and I didn't want anything to change."

Ah. That explained his relentless determination to solve this case.

"It doesn't have to," Kate promised.

"But it has," he replied, distraught. "We haven't exactly been...professional. And it's getting in the way."

"I..."

"What if the crime scene had been dangerous?" he interrupted. "What if..."

"Castle."

"We aren't on top of our game."

Kate sighed. She knew he was right. Her normally carefully bottled up control had all but evaporated since their return, and she seemed incapable of reigning herself in. Not that he was faring any better. "You're right. We aren't."

He shook his head. "We can't keep doing that. One of these days..."

"We'll figure it out," she assured him. "Maybe it'll be difficult at first, and maybe there'll be days where you stay home. But nothing has to change, Castle. Not if we don't want it to."

"Me staying home _is_ a change."

"It's only temporary," she reminded him. "Just while you get some writing done and we find our bearings again."

He still regarded her skeptically.

"Hey," Kate encouraged, rising to her knees and swinging one leg over his until she was straddling his thighs on the couch. "I'll be more professional," she whispered, looping her arms around his neck. "Starting tomorrow."

He nodded, hands coming to span her hips, strong and warm against her skin as her shirt bunched up above his touch.

"I promise," she guaranteed him. "I will. We just need to settle into a slightly new normal."

Castle's eyes seemed to clear slightly at that.

"We'll figure it out," she repeated.

"We will," he murmured in agreement. Kate offered an approving smile in return.

"In the meantime," she snagged her lower lip between her teeth, eyes flicking down to his mouth, back to his eyes.

"In the meantime..." he echoed.

"There are some very _unprofessional_ things I'd like to do to you."

He raised an eyebrow. "Yeah?"

She leaned in, tongue peeking out to wet her lips as she neared, and he felt his eyes fall close as her warm breath mingled with his. "Yeah."

* * *

They entered the precinct the next morning side by side, but with a carefully maintained amount of space between them. Their shoulders didn't brush as they stepped out of the elevator and Castle turned and headed for the break room without a lingering trail of his fingers over her arm or lower back.

She missed his touch immensely but forced herself to ignore the seeming emptiness.

When he reappeared at her desk a few minutes later, he passed her a mug of coffee, careful not to brush her fingers with his own. She offered him a genuine smile, eyes holding only briefly before flicking back to her desktop. She raised the mug to her lips, smiling around the ceramic rim as the hot liquid washed down her throat, rich and delicious. Just the way she liked it. She chanced a glance at her husband, but he was preoccupied with his own caffeine fix.

Castle set aside his mug long enough to discard his jacket and sink into his chair before turning his attention away from his wife and to the murder boards.

Kate spent a few minutes checking her email, scanning the CSU reports from their search of the sports bar and bathroom. A public place always meant a lot more work combing through all the dozens of fingerprints and other potential forensic evidence, not to mention the nasty conglomeration of substances present in the typical public bathroom. But despite the length of the report, nothing appeared to be out of the ordinary. No hidden signs of a struggle, and traces of blood found on the walls weren't a match to Annalise.

Background checks on employees from the bar had only turned up a couple of traffic tickets and a public urination violation - none of which particularly hinted towards violence or anything of the sort.

With no leads from either set of reports, Kate reached for her phone and dialed Sara's number. The girl answered on the third ring, sounding just as distraught as she'd appeared the last time they'd visited her. She was, however, able to pass along the names and contact information of the three friends she'd run into that night; Mark Johnson, Travis Duncan, and Caroline Owens.

"Wait," Castle interjected, leaning over his wife's shoulder to read the list of names and phone numbers hastily jotted down on a pad of paper. "Didn't we talk to a Caroline Owens at the sports bar yesterday?"

She consulted the list of background checks, sifting through the pages and scanning the names. "Yeah, there." Castle's finger shot out, pausing her search. "Wait, go back a page." Kate obliged. "And there. Travis Duncan. I don't think we talked to him, but he works there too.

She pursed her lips as she scanned the pages. "That can't be a coincidence."

* * *

"Thank you for coming in," Kate greeted gently, indicating for the three young adults to take a seat in the conference room.

They sank into chairs, folding their jackets across their laps. "So we're here because of Sara?" Caroline inquired curiously.

"Actually, it's Sara's roommate," Castle corrected as Kate slid a photograph across the coffee table. "Jenna."

Caroline tucked a strand of straight blonde hair behind her ear, leaned forward for a closer look. "I don't know her. Is she okay?"

"She was murdered," Kate answered. "The night you were out with Sara."

"That's awful." Caroline glanced to her friends, who looked equally shocked.

"Murdered?" Mark interjected.

"Right after you all left the bar," Castle explained.

"Did any of you know her?"

All three shook their heads. "Sorry, no," Mark verbalized.

"I didn't even know Sara that well, to be honest," Caroline added. "Travis just introduced us a few months back."

"Did anyone see anything out of the ordinary while you were there?" Castle asked, eyes falling on each person in turn.

"I...I don't think so," Caroline answered.

"I remember her talking to a girl I didn't know," Mark recalled. He gestured to the photograph. "I guess it was probably her."

"Did anything seem odd? Could you hear what they were talking about?"

He shook his head. "It was crowded. And I only saw her for a bit." He turned to Travis. "You're the one who talked to Sara, right?"

"Yeah but I never met her friend."

"And then you invited her out with you, is that correct?" Kate asked.

Caroline nodded. "Some place quieter. So we could catch up, you know?"

"Just Sara? Not Jenna?"

"Sara invited her. Said she didn't wanna come," Travis offered.

"And then what happened?" Kate asked, pen hovering over her pad of paper, poised to reconstruct what she could of the timeline.

Mark shrugged. "We left."

"Right away?"

"Pretty much," Caroline agreed. "Why?"

"Well, because Jenna died shortly after."

"And what? You think one of us had something to do with it?" Travis burst out angrily.

"We're just trying to figure out what happened," Kate placated. "And the timing of events is important."

"Right, sorry," he replied gruffly. The photo from his personnel file confirmed that this was definitely the same Travis Duncan that worked at the sports bar. It was suspicious at best, and he definitely wasn't winning himself any bonus points right now. Then again, Caroline's caring, open, wanting to help out in any way possible act was pretty transparent as well.

"I'm sorry, I wish I could be more helpful," Caroline offered gently, and Castle rolled his eyes. "But we were only there for twenty minutes or so."

"I have to ask, but where were you between two and four a.m. that night?"

"We swung by this club on Delancey for a few minutes and then went back to Mark's place," Caroline answered.

"All three of you?"

Mark nodded in corroboration.

"Anything else you can think of?"

"Sorry, no," Caroline answered, the others nodding in agreement.

"Okay, well thank you for your time," Kate said graciously. She rose, passing a card to each of them. "If you think of anything else, please give me a call."

They stood, paused to don their jackets before filing out the conference room where uniforms were waiting to escort them to the elevator.

"So what do you think?" Castle asked the moment they were out of earshot.

"I think that with all the people there, it'll be hard to verify their alibis," she answered truthfully.

"But what about Caroline and Travis?"

"I think it's definitely suspicious." Castle snorted. "But we don't have any proof it was either of them. For all we know, someone else set one of them up to take the fall."

"Or they were in on it together."

"Even if they were, what's their motive?"

"Jealousy? Who knows. They're obviously hiding something."

Kate shook her head. "Well, we'll have unis try to verify their alibis and maybe they'll shake something up in the process."

At least, she hoped that was what happened. They were starting to run out of options.

* * *

_Thoughts?_


	14. Chapter 14

_Author's Note: Apologies for the delay & thank you all for sticking with me!_

* * *

**Chapter 14**

Kate was just setting aside her notepad, poised to add their newly-acquired information to the murder boards when L.T. arrived at her desk, extending a piece of paper with a smile before heading off in pursuit of his next task.

"What's that?" Castle asked, shifting his attention. He carefully set aside his coffee mug to avoid spillage, leaned in to read the sheet of paper in her hands. He had to tilt his neck at an awkward angle, and Kate finally took pity on him, re-angled the sheet so he could read it too.

"Huh. CSU found a vial in the dumpster outside the sports bar that tested positive for aconite residue."

"Well, now we know for certain _where_ Annalise was poisoned," he offered. "Which probably means it was Travis and Caroline."

Kate consulted the file. "Actually, prints on the outside of the glass are a match to one Julian Mercado." She reached out to slap a picture up under the POTENTIAL SUSPECTS category. "Twenty five. Picked up last year for possession of a controlled substance."

"Okay, maybe it _was_ a set-up," Castle conceded. "Though you'd think he wouldn't leave his own prints on the vial."

"He doesn't seem to have any connection to Jenna," Kate mused, scanning the rest of the file.

"That our guy?" Ryan questioned, nodding to the newly added photo as he stepped up beside Kate, nursing a steaming mug of coffee.

"Possibly. CSU found his prints on a vial of aconite."

He raised his eyebrows. "Sounds like a good bet."

Kate nodded in agreement, passed him the file. "You guys see what you can dig up on his arrest. Castle and are gonna go have a chat with him, see why his prints were on that vial."

Ryan tilted his head in acknowledgement. "On it."

* * *

"Mr. Mercado?" Kate called as they strode into the carwash at which records indicated Julian worked. She glanced around for anyone resembling the mug shot. "Julian?"

Off to the left, a head snapped up. Wide dark eyes locked with Kate's for just a moment before he tossed aside the towel in his hand and bolted.

"Hey, stop," Kate called out, already racing after him. "Police."

Castle took off after her, flaps of his jacket flying out to the sides as he raced out of the garage and across the parking lot. Kate was well ahead of him, catching up to Julian easily when a line of cars came to a stop at a traffic light, halting his progress. She tackled him to the ground, digging her knee into his back as she jerked his hands behind him, snapped on the cuffs.

Castle stopped a few feet away to catch his breath, beaming in pride as Kate dragged their suspect to his feet, began shuttling him towards her cruiser.

He had the most badass wife in all of New York City.

* * *

"So, Julian, why'd you run?"

"You're a cop," Julian replied, leaning forward in a gesture Castle assumed was meant to be intimidating. The creepy neck tattoo certainly added to the image, but the fact that one hand was cuffed to the table and he was bearing a scrape on the side of his head from hitting the ground negated the effect. "Been busted before."

"Generally, running from cops is a good way to get busted again," Castle pointed out. Kate shot him a withering look and he fell silent.

"Why am I here?"

"You're here because your fingerprints were found on a vial of poison," she answered, pushing a forensic photo of the tiny glassware across the table. "Poison that was used to commit a murder."

"I didn't kill nobody."

"Then you mind explaining how your fingerprints got there?"

Julian shrugged. "Dunno."

"Really?" Kate challenged. "Because no two people have identical fingerprints."

"Maybe there's some mistake."

"There's no mistake," Castle replied flatly.

He snorted. "Please. There's no way you're a cop."

"I..."

"Prior conviction for possession and a prime suspect for my murder case," Kate interrupted. "You better start talking."

Upon receiving no answer, she began to collect her things, stood to leave the room.

"Fine, I seen the vial."

She sank back into her chair, folded her hands on the table top. "Where?"

When he didn't answer, Kate's eyes narrowed in challenge. Julian sighed heftily, relented. "In my apartment."

"And what was it doing there?"

"Buddy of mine said he needed it. Said his mom was goin' through some stuff and he read somewhere it'd help with the pain."

"This buddy of yours have a name?"

"Why should I tell you?"

She opened her folder once again, fingers tapping ominously over the photo of the vial. "Look, I don't care about the drugs. What I _do_ care about is the young woman who was poisoned. We have _your_ fingerprints on the vial. How do you think that looks for you?"

"I didn't kill nobody. I'm telling you." Julian protested.

"Then who'd you give the poison to?"

"I didn't know he was gonna kill anyone. I swear."

"Who did you give it to?" she enunciated sharply.

Another tense silence filled the room before Julian finally shriveled under Kate's menacing stare.

"Travis Duncan."

* * *

"So he's friends with Sara, supposedly received the aconite from our boy in interrogation, and just happens to work at the place where Annalise was killed?" Ryan recited suspiciously, glancing over to his partner as they watched from the observation room.

Espo turned, already reaching for the doorknob with Ryan hot on his heels. "Let's see what else we can find."

* * *

"Boom, got something," Esposito announced a few minutes later.

Kate and Castle were on their feet right away, striding to his desk. He swiveled around his computer monitor as they approached, revealing the information on the screen.

"Travis Duncan. Grew up in Brooklyn, parents were in and out of jail on a pretty regular basis, from the looks of it. Raised by his aunt and uncle. Also living with them was their biological daughter..."

He scrolled down to reveal a name and photograph. "Carly Mathers."

"The girl who died in the car wreck?" Castle asked in surprise.

Kate folded her arms across her chest, bent forward to better read the information on the screen before straightening her shoulders. "Bring him back in."

* * *

"I already told you. I didn't kill anyone."

Travis was a twenty-something red head, dressed in jeans and a Yankees t-shirt, with a dark blue hooded sweatshirt tossed over the back of the chair. He'd been anything but truthful since Kate and Castle's arrival in the interrogation room. He'd also remained oddly calm, seemingly unfazed by this impromptu trip to the Twelfth.

Kate slapped a photo of Jenna down on the table in front of him. "So you've really never seen this woman before?"

He squinted one eye in irritation. "No. Not before you showed me her picture this morning."

A picture of Annalise. "How about her?"

"No. Who's she?"

Castle slid an additional two photos across the table, the shiny rectangles coming to rest atop the other two. "They're friends of these two."

He hesitated slightly but covered it well. "I don't know them either."

"Really? Because just this morning you claimed to know Sara."

Travis glanced at the picture again. "Oh. Yeah, I know her. Not the other guy though. Never seen him before."

"I find that hard to believe, considering that both of them were involved in the same car accident as your cousin."

"The one that killed her," Castle added.

Kate opened the file on Carly's death and Travis's eyes immediately fixated on the pictures from the scene.

"What's Carly got to do with all of this?"

"She was like a sister to you," Castle profiled.

"Course she was. We grew up together. But I had nothing to do with that accident."

"We know," Kate assured him. "But Sara and Ernesto," she indicated the photographs, "they were in the car with her. They were the ones who could've prevented it."

"Because of them, your cousin is dead," Castle continued. Sara had been cleared of all charges in the accident, but it was blatantly evident that Travis disagreed with that ruling. "And they walked away scot free."

"So?"

"So I could see how you'd be out for revenge."

"If I wanted revenge, why wouldn't I have just killed them?" Travis challenged, nodding to the photos of Sara and Ernesto.

"In that case, you won't mind me asking where you were Saturday morning between two and four am," Kate offered, changing the subject. It was obvious they weren't going to draw out a confession, but if they could disprove his alibi, they'd have a lot more leverage.

"Already told you. I was out with Sara and them."

"And what about Sunday between five and seven pm?" Kate asked.

"I was at work."

"Right, at the same sports bar where Annalise was killed," Castle recited.

"What?"

"Come on, you're telling us you didn't see the cops swarming the place?"

"I did, but I didn't know...I swear, I had nothing to do with her death. With either of them."

Castle regarded him skeptically. "So you just happened to be there? On both occasions?"

"C'mon, man. It's Manhattan. Everyone goes out on the weekends."

Kate collected the pictures and slipped them back into the folder before emphatically shutting it, rising. "Sit tight. You're gonna be here for a while."

* * *

_Thoughts?_


	15. Chapter 15

_Author's Note: Just want to quickly thank all of you for reading & reviewing & being so lovely and supportive. You guys are the best!_

_And thank you again to Andy for the encouragement and brainstorming and ideas, and to Liv Wilder for beta-ing every single chapter and sharing her wealth of information and suggestions with me. I've learned a lot and I really appreciate all of your help!_

* * *

**Chapter 15**

"He's not gonna crack," Castle huffed in frustration as the door of the interrogation room snicked shut behind them. "We need solid proof."

"I know," she agreed. "But there were a hundred other people at the bar too, and we haven't found a single person who witnessed Travis dosing Jenna's drink. Or anything out of the ordinary, for that matter. We need more."

"Julian's alibi checks out," Espo relayed, falling into step next to Castle and Kate as they made their way across the bullpen.

Kate detoured to the break room, the guys on her heels. "Figured it would."

"So he must've been telling the truth."

Kate tilted her head, regarding Castle inquisitively. "What are you thinking?"

"Well, Julian obviously didn't know what the aconite was really for. Otherwise, he'd have made sure not to touch it."

"So Travis convinces Julian to give him the vial of aconite," she begins, collecting a clean mug and placing it under the spigot on the espresso machine.

"He wears gloves when he touches it – which, if he was at the restaurant, wouldn't have been hard to come by – but leaves Julian's prints all over it to throw us off."

"But if he was going to so much trouble to frame someone else, would he have thrown the vial away somewhere farther from the restaurant? Somewhere where we'd never find it?"

"Maybe he didn't think he'd get caught," Castle pointed out. "After all, he went to a hell of a lot of trouble to make this look accidental."

"Speaking of which," Espo cut in. "How'd he know to slip peanut oil into Jenna's drink?"

"He must've known her," Ryan hypothesized as he joined the group.

"But there's no indication of that," Kate recollected.

"Right, because only Sara was invited out with these 'friends.'" Castle curled his fingers into air quotes as he spoke. "Not Jenna."

"Maybe he knew through Sara somehow?" Ryan suggested.

Esposito shrugged. "He could've asked at some point, I suppose."

Kate sighed, picking up her now steaming mug of coffee and taking a sip. "Okay, see if you can find anything connecting Jenna to Travis. Unis are searching his apartment as we speak. Castle and I'll go back to the restaurant, see what we can dig up."

* * *

"You guys come back to make up more stories 'bout how I killed those girls?"

"They're not made up," Castle asserted firmly.

Travis scoffed. "Really? Cause all that stuff you said before sounded like a bunch of made up crap."

"Was it?" Kate challenged. "We found the vial of poison in the dumpster outside your work. The same poison used to kill Annalise. We know that it was yours."

"We also know that the restaurant uses peanut oil to make their French fries. The same brand of peanut oil was used to kill Jenna. As an employee, you'd have had easy access to it."

"Peanut oil? How am I supposed to kill someone with peanut oil?"

"She was allergic," Castle explained. "All you'd need to do is slip some in her drink."

"I told you, I didn't even _know_ her. How am I supposed to know she's allergic?"

"Oh, and then there's this. Statements from your other friends." Castle pretended to consult the file on the table. As though he didn't already know what was contained there. "Mark and Caroline. You know the ones. We spoke to them again and they said you weren't with them the whole time. No, you disappeared into the crowd for ten or fifteen minutes. Plenty of time to slip peanut oil into Jenna's drink and ditch her purse in a dumpster in the alley around the corner."

He snorted. "Please. That's ridiculous."

"After which you 'ran into' Sara and invited her out with you," Kate continued, ignoring his interjection. "Eliminating every immediate option for helping Jenna."

"There's just one thing we can't figure out," Castle bluffed, leaning forward, blue eyes serious. "Why didn't you kill Sara, too?"

Travis sat back in the chair, folded his arms over his chest and fixed them with a derisive stare. "You guys seem to have it all figured out," he snarked. "Why don't you tell me?"

* * *

"Well, Travis made a full confession," Kate announced as she exited interrogation half an hour later. She waited for him to be escorted away by uniforms before continuing. "Turns out he'd been planning this for over a year."

Castle picked up where his wife left off. "It was a tale of revenge. Carly's parents took her death hard, understandably. Her mom moved out of the house and her dad started drinking heavily. Got busted for assault and spent a couple nights in prison."

"So it was revenge on her parents' behalf?" Ryan asked, head cocked to the side in confusion.

"Seems like it, though they had nothing to do with the murders," Kate clarified. "In Travis' mind, all of it was Sara and Ernesto's fault."

"And what better way to make them pay than to take away the people closest to them?" Castle continued. "Just like they did to him."

"He took the job at the sports bar for the sole purpose of getting close to Annalise," Kate explained. "Apparently she and Ernesto frequented the place."

"He was stalking them?" Ryan interjected.

"Seems like it."

"So he waited until she showed up at the restaurant, dosed her beer with the aconite, and no one was any the wiser."

Ryan tilted his head thoughtfully. "What about Jenna?"

"He was in the process of planning this whole thing when she and a coworker happened to show up at the restaurant one day. Told him about her peanut allergy in the course of ordering her meal, and he figured that'd be an even more foolproof way to get away with killing her."

"Both of them," Castle clarified. "Make it look like an accident by slipping poison into their food."

"Or using food as a poison of sorts," Kate added, nodding to Castle.

Esposito jumped in. "Almost worked, too."

"Mmmm," she acknowledged.

"Wait, Sara didn't know Carly was Travis's cousin?" Ryan asked.

"Different last names," Kate pointed out. "Sara had no idea. Guess Travis never mentioned it."

"They knew each other from way back in school but drifted apart for a while," Castle explained.

"Reconnected a couple of years ago, when Sara mysteriously 'ran into' him at a club," Kate added.

"You think that was intentional," Ryan guessed correctly.

"Seems like it."

"And she and Carly were more of the go-out-and-have-a-good-time sort of friends than the talk-about-your-life type," Castle explained.

"And Caroline?" Espo asked.

Kate shook her head. "Didn't know anything about it."

"Small world," Ryan mused.

Kate set the case files on her desk, sank into her chair. "Small world indeed."

* * *

"It's just so unfair," Castle lamented as they dismantled the murder board, packed up the files.

"I know, Castle," she agreed.

"They were so young."

"I know," she responded again.

He shook his head, Jenna's picture clutched in his hand. "All because of an accident."

"We got him," Kate reminded him. "We found justice for their families and for Sara and Ernesto."

"That doesn't bring them back."

"No, it doesn't," she murmured sadly, eyes dropping to the photograph of Jenna. Two young, smart, beautiful women taken from this world far too soon, and all because of some misplaced anger.

"But hey," she began hesitantly, slipping the picture from his grasp and placing it in the box with the rest of the materials from the two murder boards. "We solved the case. We proved that we can do this."

"We did," he agreed proudly. It wouldn't be easy, and he knew they'd both likely find themselves fighting to hold back. But they'd proven today that they could do this. They could be married and still be professional, still solve crimes.

"We're gonna make this work," she assured him. "I promise."

"Yeah?"

Kate secured the lid on the box, smiled gently. "Yeah."

* * *

"How's Alexis doing?" Kate murmured as Castle slipped into bed behind her, setting aside his phone before extending his legs under the covers and molding his body to hers from behind.

"She's fine. Still thinks I'm overreacting, but she promised to be careful and that she'd always call if something seemed suspicious."

Kate nodded into the pillow. "Good."

"You think I'm overreacting too," he profiled.

She rolled onto her back, turned her head to face him. "I think that you can be over protective," she admitted. His face fell but she stopped him with her next words. "But it makes me feel safe. And loved."

"You are."

"I know, Castle." She smiled, a dazzling, beautiful thing, couldn't reign in her emotions. The things he did to her, even after all this time. "I'm pretty damn lucky."

He dipped his chin to capture her lips in a deep kiss, melding everything he couldn't find the words for into the tender, loving gesture. Six years and he still found himself at a loss of words. "No, Kate. I'm the lucky one."

* * *

**END**


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